[Tutor] File mode r+
Hi,
I want to update a textfile using the r+ file mode.
contents of file:
abcd
efgh
ijkl
mnop
qrst
uvwx
yx12
my scripts is:
file1=open("aa.txt",'r+')
file1.readline()
file1.readline()
file1.write("1234\n")
file1.close()
This should replace the third line with 1234.
However it does nothing.
Moreover the script:
file1=open("aa.txt",'r+')
file1.write("1234\n")
file1.close()
does replace the first line with 1234.
could anyone explain what is happening?
shitiz
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Re: [Tutor] Binary 2 text & text 2 binary
If your symbol are specific it is better to use dictionary.
then if the user give an input you can take character by character and translate into your binary.
This is the code textTobinary:
mydic = {'A' : "0101", 'B' : "0110", 'C' : "0111"} strinput = 'ABBC' result = [mydic[x] for x in strinput_process] print result
Cheers,
pujo
On 9/24/05, Joseph Quigley <[EMAIL PROTECTED]> wrote:
Hi I'm playing with a Binary to text & text to binary converter. I can'tfigure out how to replace the characters (first stage: text to binary).
I thought lists would be the best but I really don't know how to usethem... here's my code:#! /usr/bin/env pythonA = "0101"B = "0110"C = "0111"D = "01000100"
E = "01000101"F = "01000110"G = "01000111"H = "01001000"I = "01001001"J = "01001010"K = "01001011"L = "01001100"
M = "01001101"N = "01001110"O = "0100"P = "0101"Q = "01010001"R = "01010010"S = "01010011"T = "01010100"
U = "01010101"V = "01010110"W = "01010111"X = "01011000"Y = "01011001"Z = "01011010"# SymbolsexclamationPoint = "0010 0001"
hash = "0010 0011"dollar = "001 0100"percent = "0010 0101"_and = "0010 0110"parentheses = "0010 1000"closeParentheses = "0010 1001"comma = "0010 1100"
dash = "0010 1101"period = "0010 1110"underline = "0101 "# Numberszero = "0011">two = "00110010"three = "00110011"
four = "00110100"five = "00110101"six = "00110110"seven = "00110111"eight = "00111000"nine = "00111001"ltra = "a"ltrb = "b"
ltrc = "c"while True: text = raw_input("Enter text: ") text = list(text)Thanks, Joe___Tutor maillist -
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Re: [Tutor] Help with pi and the math module.
hi, if you use : import math you can type: diameter * math.pi if you use from math import * you can type: diameter * pi Cheers, pujo On 9/24/05, Nathan Pinno <[EMAIL PROTECTED]> wrote: Hi all, I need help with pi and the math module. I had import math at the top of a program, but when it came to diameter*pi, it said that pi was not defined. How do I use it correctly? Thanks, Nathan Pinno___Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Binary 2 text & text 2 binary
Pujo Aji wrote:
> If your symbol are specific it is better to use dictionary.
> then if the user give an input you can take character by character and
> translate into your binary.
> This is the code textTobinary:
> mydic = {'A' : "0101", 'B' : "0110", 'C' : "0111"}
> strinput = 'ABBC'
> result = [mydic[x] for x in strinput_process]
> print result
>
You might also want to look at "Number to String in Arbirtrary Base" recipe:
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/365468
It uses a more innovative approach.
--
Poor Yorick
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Re: [Tutor] Using new style classes and __slots__
mailing list wrote: > Hi all, > > I'm just looking for a quick runthrough on the differences between new > style classes and the old ones, and how to use the new ones. > > Also, how exactly do you use __slots__? I've got a 6000 object > collection, and apparently using __slots__ will save memory, but only > those attributes specified in __slots__ can be set, which suits my > project fine. All you have to do is define a __slots__ variable in your class. Its value is a list of attribute names. Then instances of your class will only be able to have the attributes named in __slots__: >>> class foo(object): ... __slots__ = ['x', 'y'] ... >>> f=foo() >>> f.x=1 >>> f.y=2 >>> f.z=3 Traceback (most recent call last): File "", line 1, in ? AttributeError: 'foo' object has no attribute 'z' Take a look at http://www.python.org/2.2.3/descrintro.html (search for __slots__) Note to the list: Use of __slots__ is generally discouraged, but IIUC this is exactly the use case it was designed for so I think it is OK. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Using new style classes and __slots__
Hi Kent, > > >>> class foo(object): > ... __slots__ = ['x', 'y'] > ... > >>> f=foo() > >>> f.x=1 > >>> f.y=2 > >>> f.z=3 > Traceback (most recent call last): > File "", line 1, in ? > AttributeError: 'foo' object has no attribute 'z' > > Take a look at > http://www.python.org/2.2.3/descrintro.html (search for __slots__) Thanks for that. I was tearing my hair out trying to figure out why despite the usage of __slots__ my instances still had a __dict__, and then I saw the subclass of object, and sure enough... I'm guessing that's how you get new style classes. Quite like what I'm seeing, __slots__ and that property() thing will allow me to remove all my __setattr__ and __getattr__ methods, which tend to make things crawl a wee bit. I was almost considering writing setters/getters to get around the magic methods, but I grew to dislike them after having used Java, I got annoyed at having to write setters/getters for every public variable. Of course, I was using Notepad to write the Java programmes, and then Eclipse helped me realise why Java programmers value IDE's so much, it's that automatic generation of set/gets... > Note to the list: Use of __slots__ is generally discouraged, but IIUC this is > exactly the >use case it was designed for so I think it is OK. Throwing an error on adding a new attribute is just what I need as the data I'm reading/writing has a very specific format; instead of using __setattr__ and checking that the attribute already existed, I can just let __slots__ do the work. Out of curiosity, if you're using __slots__ with new style, you no longer have __dict__. So, where does it stick data? I was using 'self.__dict__["_created"] = False' to set a flag at the start of __init__ to stop __setattr__ picking up the attributes being set from parsed data (and running all my type checks, etc.), but I won't need that anymore. I could almost hug property(). :) All in all, this has been an interesting tour around the inner workings of a class in Python. Give it another five years, I might be able to read one of those metaclass explanations and understand it. Regards, Liam Clarke PS Just for my edification, is there a builtin to determine how much memory is allocated to an object? ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Using new style classes and __slots__
mailing list wrote: > Hi Kent, > > > >> >>> class foo(object): >> ... __slots__ = ['x', 'y'] >> ... >> >>> f=foo() >> >>> f.x=1 >> >>> f.y=2 >> >>> f.z=3 >>Traceback (most recent call last): >> File "", line 1, in ? >>AttributeError: 'foo' object has no attribute 'z' >> >>Take a look at >>http://www.python.org/2.2.3/descrintro.html (search for __slots__) > > > Thanks for that. I was tearing my hair out trying to figure out why > despite the usage of __slots__ my instances still had a __dict__, and > then I saw the subclass of object, and sure enough... I'm guessing > that's how you get new style classes. Yes, exactly. To be precise: A class is a new-style class if its metaclass is type 'type' or inherits from type. If you inherit from a new-style class, your class will have the same metaclass as the base class and thus be a new-style class. The simplest way to do this is to inherit from object. > Quite like what I'm seeing, __slots__ and that property() thing will > allow me to remove all my __setattr__ and __getattr__ methods, which > tend to make things crawl a wee bit. That's exactly what property() is for. > I was almost considering writing setters/getters to get around the > magic methods, but I grew to dislike them after having used Java, I > got annoyed at having to write setters/getters for every public > variable. Of course, I was using Notepad to write the Java programmes, > and then Eclipse helped me realise why Java programmers value IDE's > so much, it's that automatic generation of set/gets... One of the cool things about properties is that you can start with simple attributes and change them later to have behaviour without having to change the client code or use getters and setters all the time. > Out of curiosity, if you're using __slots__ with new style, you no > longer have __dict__. So, where does it stick data? My understanding is that there are actually 'slots' allocated in the object to hold the references to the attribute data, kind of like a C struct. I'm not sure about this though. > I was using 'self.__dict__["_created"] = False' to set a flag at the > start of __init__ to stop __setattr__ picking up the attributes being > set from parsed data (and running all my type checks, etc.), but I > won't need that anymore. I could almost hug property(). :) You might want to learn more about the whole property mechanism then. property() is actually a bit of sugar over a deeper mechanism. Also there is an interesting idiom for creating properties using @apply (in Python 2.4) - look for Benji York's comment in this recipe: http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/410698 > > All in all, this has been an interesting tour around the inner > workings of a class in Python. > Give it another five years, I might be able to read one of those > metaclass explanations and understand it. Me too! Kent > > > Regards, > > Liam Clarke > > PS Just for my edification, is there a builtin to determine how much > memory is allocated to an object? > ___ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor > > ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Sum of List Elements
Hi All, I have spent an embarrassingly large amount of time trying to solve what on its face seems like a simple problem. I have a list of intergers, and I want to assign the sum of the intergers in the list to a variable. There are only intergers in the list. The best I have been able to do so far is to write a function that adds list[0] and list[1], then list[1] and list [2], etc. Of course, this isn't what I want. I'd like to be able to sum a list of any size without having to type list[0]+list[1] I am totally stumped. :( Luke -- "Whether you're an honest man, or whether you're a thief, depends on whose solicitor has given me my brief. " - Benjamin Franklin ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Sum of List Elements
> Hi All, > I have spent an embarrassingly large amount of time trying to solve what on > its face seems like a simple problem. > I have a list of intergers, and I want to assign the sum of the intergers in > the list to a variable. There are only intergers in the list. > The best I have been able to do so far is to write a function that adds > list[0] and list[1], then list[1] and list [2], etc. Of course, this isn't > what I want. > I'd like to be able to sum a list of any size without having to type > list[0]+list[1] total=0 for x in list: total += x ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Binary 2 text & text 2 binary
Hi,
>From: "R. Alan Monroe" <[EMAIL PROTECTED]>
>
>They're easy. Just put stuff in square brackets with commas between.
>
>mycoollist = [1,5,9,3,6,9,2,6]
>mystringlist = ['a', 'u', 'e', 'b', 'd', 'h', 'q', 't']
>
>
Ah sorry I forgot to say: I know how to print them but that's about it.
>Can you predict what this code will do?
>print mycoollist[0]
>
>
yes. It will print (edited) [1, 2, 3 ,4 ]
I'll rephrase myself again: I'd like to know where I can find tutorials
for slicing or some help from any of you. However keep on reading and I
think I'll have my answer :-)
>Message: 11
>Date: Sat, 24 Sep 2005 10:42:13 +0200
>From: Pujo Aji <[EMAIL PROTECTED]>
>
>If your symbol are specific it is better to use dictionary.
>
>
Good Idea! Thanks
>then if the user give an input you can take character by character and
>translate into your binary.
>This is the code textTobinary:
> mydic = {'A' : "0101", 'B' : "0110", 'C' : "0111"}
>strinput = 'ABBC'
>result = [mydic[x] for x in strinput_process]
>print result
>
>
>
This helps a lot, thank you!
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Re: [Tutor] Sum of List Elements
how about sum()? >>> sum(range(30)) 435 -Bill ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Sum of List Elements
Also, the built in function sum(): total = sum(list) Which is probably the One Obvious Way since 2.3, if I had to guess. On 9/24/05, R. Alan Monroe < [EMAIL PROTECTED]> wrote:> Hi All,> I have spent an embarrassingly large amount of time trying to solve what on > its face seems like a simple problem.> I have a list of intergers, and I want to assign the sum of the intergers in> the list to a variable. There are only intergers in the list.> The best I have been able to do so far is to write a function that adds > list[0] and list[1], then list[1] and list [2], etc. Of course, this isn't> what I want.> I'd like to be able to sum a list of any size without having to type> list[0]+list[1] total=0for x in list:total += x___Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] File mode r+
At 01:11 AM 9/24/2005, Shitiz Bansal wrote:
>Hi,
>I want to update a textfile using the r+ file mode.
>contents of file:
>
>abcd
>efgh
>ijkl
>mnop
>qrst
>uvwx
>yx12
>
>my scripts is:
>
>file1=open("aa.txt",'r+')
Instead of readline, use skip to position the file to where you want to
overwrite it.
file1.seek(10)
>file1.readline()
>file1.readline()
>file1.write("1234\n")
>file1.close()
>
>This should replace the third line with 1234.
>However it does nothing.
>
>Moreover the script:
>
>file1=open("aa.txt",'r+')
>file1.write("1234\n")
>file1.close()
>
>does replace the first line with 1234.
>
>could anyone explain what is happening?
>
>shitiz
>
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Re: [Tutor] Stupid newbie question
As long as you are using IDLE, why not let it handle indentation for you? This could very well be a dumb question, and if it is, well, excuse me :)On 9/23/05,
Valone, Toren W. <[EMAIL PROTECTED]> wrote:
I am trying to noodle thru classes with python and I built the followingclassimport timeclass startremail:def __init__(self): remailfile = open('U:\Bounce20.txt', 'r') #future
address/file from outlook resendfile = open('resend.txt', 'w') #currently thesefiles are in Python24 EmailReport = open('erprt.txt', 'w') #Report of bademails etc
fromaddr='[EMAIL PROTECTED]' #set fromadd to aconstant null_recepient_count = 0 date_received = "" date_email_generated = ""
Error_050 = "" Error_501 = "" Current_Date = time.ctime(time.time()) month = Current_Date[4:8] day = Current_Date[8:10] print month def getday(self):
return self.day def Read(self,line): line = remailfile.readline() #primer read return lineI fire up IDLE and then do thisfrom startremail import *
x = startremail()print x.getday()I get the following returnNameError: name 'getday' is not defined___Tutor maillist -
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Re: [Tutor] Sum of List Elements
At 08:11 AM 9/24/2005, Luke Jordan wrote: >Hi All, > >I have spent an embarrassingly large amount of time trying to solve what >on its face seems like a simple problem. > >I have a list of intergers, and I want to assign the sum of the intergers >in the list to a variable. There are only intergers in the list. In addition to the other solutions there is the (more generic?) use of the operator module and reduce function: import operator reduce(operator.add, (1,2,3)) Explore operator to see what other functions you can use. Also there are the array handling modules such as numarray. You can also define your own classes based on list and write methods to do these operations. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Sum of List Elements
Thanks for the help everyone, for answering a simple question and pointing me toward more resources.On 9/24/05, bob < [EMAIL PROTECTED]> wrote:At 08:11 AM 9/24/2005, Luke Jordan wrote:>Hi All, >>I have spent an embarrassingly large amount of time trying to solve what>on its face seems like a simple problem.>>I have a list of intergers, and I want to assign the sum of the intergers >in the list to a variable. There are only intergers in the list.In addition to the other solutions there is the (more generic?) use of theoperator module and reduce function:import operator reduce(operator.add, (1,2,3))Explore operator to see what other functions you can use.Also there are the array handling modules such as numarray.You can also define your own classes based on list and write methods to do these operations.-- "Whether you're an honest man, or whether you're a thief, depends on whose solicitor has given me my brief. " - Benjamin Franklin ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] File mode r+
Hi,
How do i proceed if i am not sure about the number of characters in the fist two lines and want to write in the third line.is there a way to skip two lines and write on the third??
Also could anyone explain why the readline() did not work. according to what i understand it should.
shitizbob <[EMAIL PROTECTED]> wrote:
At 01:11 AM 9/24/2005, Shitiz Bansal wrote:>Hi,>I want to update a textfile using the r+ file mode.>contents of file:>>abcd>efgh>ijkl>mnop>qrst>uvwx>yx12>>my scripts is:>>file1=open("aa.txt",'r+')>>Instead of readline, use skip to position the file to where you want to >>overwrite it.>>file1.seek(10)
>file1.readline()>file1.readline()>file1.write("1234\n")>file1.close()>>This should replace the third line with 1234.>However it does nothing.>>Moreover the script:>>file1=open("aa.txt",'r+')>file1.write("1234\n")>file1.close()>>does replace the first line with 1234.>>could anyone explain what is happening?>>shitiz>>__>Do You Yahoo!?>Tired of spam? Yahoo! Mail has the best spam protection around>http://mail.yahoo.com>___>Tutor maillist - Tutor@python.org>http://mail.python.org/mailman/listinfo/tutor
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Re: [Tutor] Using new style classes and __slots__
Hi, > You might want to learn more about the whole property mechanism then. > property() is actually a bit of sugar over a deeper mechanism. Also there is > an interesting idiom for creating properties using @apply (in Python 2.4) - > look for Benji York's comment in this recipe: > http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/410698 Thanks Kent. Just looking at that above recipe, I'm not too sure how the @ decorators work. >From what I understand, it defines would turn apply() into a function that returns the various get/sets? Also found something interesting with property(), if it's called in __init__ you get >>> a.a whereas called outside __init__ it works normally. This is a hassle for me because I'm a lazy typist, so I've been using setattr() to pull attribute names out of a list. And the first argument setattr() requires is an object, and self doesn't work outside of a method, and using the class name leads to no attribute being set. Hmm, may have to learn even more about classes and their internals. Regards, Liam Clarke ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] (no subject)
Hello
How would I get the following program to accept inputs of exam scores from 0-100 with A being 100-90, B being 89-80, C being 79-70, D being 69-60, and F being everything less than 60?
import string
def main():
scores = ["F", "D", "C", "B", "A"]
g = input("Enter a score number (0-100): ")
print "The score of your exam is", scores [g-0] + "."
main()
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[Tutor] printing an acronym
Hello
How could I get the following to print out an acronym for each phrase
entered such as if I entered random access memory it word print out RAM?
import string
def main():
phrase = (raw_input("Please enter a phrase:"))
acr1 = string.split(phrase)
acr2 = string.capwords(phrase)
acr3 = acr2[0]
print"",acr3
main()
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Re: [Tutor] printing an acronym
> Hello
> How could I get the following to print out an acronym for each phrase
> entered such as if I entered random access memory it word print out RAM?
> import string
> def main():
> phrase = (raw_input("Please enter a phrase:"))
> acr1 = string.split(phrase)
> acr2 = string.capwords(phrase)
> acr3 = acr2[0]
> print"",acr3
> main()
What does it currently print?
The typical way would be to use a for loop on acr1.
Alan
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Re: [Tutor] (no subject)
At 03:29 PM 9/24/2005, [EMAIL PROTECTED] wrote:
Hello
How would I get the following program to accept inputs of exam scores
from 0-100 with A being 100-90, B being 89-80, C being 79-70, D being
69-60, and F being everything less than 60?
Many solutions are available. One could use an if statement:
if g >= 90: s = 'A'
elif g >= 80: s = 'B'
...
else: g = 'F'
although that can be hard to
maintain.
Or associate the lower limit with the data and search using a
loop:
scores = [("A",90), ("B",80), ("C".70),
("D",60),("F",0) ]
for letter, number in scores:
if g >= number:break
print "The score of your exam is", letter
This separates the data from the program structure and becomes much
easier to maintain / extend, apply to new situation.
If you are using a database then you could store these value pairs in a
table and use SQL to retrieve the desired letter.
When the number ranges have a nice progression, you can reduce the number
to an index:
print "The score of your exam is",
"FEDCBAA"[g/10] # this is simpler code but harder to
read/maintain.
Or - knowing that chr(65) = "A", chr(66) = "B" you
could convert the number to be in the range 65..70 and use
chr()
import string
You do not refer to the string module, so there is no need to import it.
Also be ware that it will eventually go away.
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Re: [Tutor] Using new style classes and __slots__
Ooer, Well, I got setattr() and property() working together nicely, but with a weird side effect. class Strange(object): def getA(um, self): print "What is", um return self.__a def setA(um, self, value): print um, "turns up here as well." self.__a = value def __init__(self): setattr(Strange, "a", property(self.getA, self.setA)) self.a = 20 >>> c = Strange() <__main__.Strange object at 0x01166290> turns up here as well. >>> print c.a What is <__main__.Strange object at 0x01166290> 20 >>> c <__main__.Strange object at 0x01166290> To my uneducated eye, it looks like it's passing self twice! Returning um.__a works exactly the same as self.__a! I'm getting the feelin I may need to venture into comp.lang.Python with this sort of stuff. Interesting. Liam Clarke On 9/25/05, Liam Clarke <[EMAIL PROTECTED]> wrote: > Hi, > > > > You might want to learn more about the whole property mechanism then. > > property() is actually a bit of sugar over a deeper mechanism. Also there > > is an interesting idiom for creating properties using @apply (in Python > > 2.4) - look for Benji York's comment in this recipe: > > http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/410698 > > Thanks Kent. Just looking at that above recipe, I'm not too sure how > the @ decorators work. > From what I understand, it defines would turn apply() into a function > that returns the various get/sets? > > Also found something interesting with property(), if it's called in > __init__ you get > >>> a.a > > > whereas called outside __init__ it works normally. > > This is a hassle for me because I'm a lazy typist, so I've been using > setattr() to pull attribute names out of a list. And the first > argument setattr() requires is an object, and self doesn't work > outside of a method, and using the class name leads to no attribute > being set. > > Hmm, may have to learn even more about classes and their internals. > > Regards, > > Liam Clarke > ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Using new style classes and __slots__
Liam Clarke wrote: >>http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/410698 > > > Thanks Kent. Just looking at that above recipe, I'm not too sure how > the @ decorators work. >>From what I understand, it defines would turn apply() into a function > that returns the various get/sets? OK, lets pick it apart a bit. Here is the recipe for defining a property: class Example(object): @apply def myattr(): doc = """This is the doc string.""" def fget(self): return self._value def fset(self, value): self._value = value def fdel(self): del self._value return property(**locals()) Looking at myattr(), it defines the four attributes that make a property - doc, fget, fset and fdel. So at the end of myattr(), locals() is a dictionary containing these four attributes. Then it calls property() and passes it locals() as keyword arguments. So the last line is the same as return property(doc=doc, fget=fget, fset=fset, fdel=fdel) which creates a normal property. OK, now what does the @apply do? Well, it's a decorator, and in general @some_decorator def myfunc(): # etc means the same thing as def myfunc(): # etc myfunc = some_decorator(myfunc) In other words the decorator is called with the function as an argument, and the return value of the function is bound to the name of the original function. So we have to know what apply(myattr) does. Actually, it just calls myattr(). So the net result is myattr = myattr() i.e. myattr = property(doc=doc, fget=fget, fset=fset, fdel=fdel) which is what you would have done any way if you weren't trying to be so clever. What does this recipe buy you? It puts the property function definitions into a separate namespace so they are not accessible as member functions, and it lets you reuse the names for them instead of having to invent new ones each time. > > Also found something interesting with property(), if it's called in > __init__ you get > a.a > > > > whereas called outside __init__ it works normally. Are you assigning the property to self or to the class? It might work if you assign to the class. But you will be recreating the properties for every instance. > > This is a hassle for me because I'm a lazy typist, so I've been using > setattr() to pull attribute names out of a list. And the first > argument setattr() requires is an object, and self doesn't work > outside of a method, and using the class name leads to no attribute > being set. I don't understand this at all, can you give an example? > > Hmm, may have to learn even more about classes and their internals. Yeah, it sounds like maybe a case for a metaclass. Kent > > Regards, > > Liam Clarke > ___ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor > > ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Using new style classes and __slots__
Your method signatures are off. Should be def getA(self): def setA(self, value) So when you write self.a = 20 you are passing self as the um parameter. Actually I don't know why you don't get an exception for passing too many arguments? And you don't need setattr, just write Strange.a = property(...) Oh wait, I get it - you are passing bound methods to property(). So um is bound to the instance when you access self.getA. Use Strange.getA instead of self.getA, then use the normal signatures. But I don't get why you are doing this at all? What does it buy you over the standard form of class Normal(object): def getA(self): return self.__a def setA(self, value): self.__a = value a = property(getA, setA) def __init__(self): self.a = 20 One more note below. Kent Liam Clarke wrote: > Ooer, > > Well, I got setattr() and property() working together nicely, but with > a weird side effect. > > class Strange(object): > def getA(um, self): > print "What is", um > return self.__a > > def setA(um, self, value): > print um, "turns up here as well." > self.__a = value > > def __init__(self): > setattr(Strange, "a", property(self.getA, self.setA)) > self.a = 20 > > c = Strange() > > <__main__.Strange object at 0x01166290> turns up here as well. > print c.a > > What is <__main__.Strange object at 0x01166290> > 20 > c > > <__main__.Strange object at 0x01166290> > > To my uneducated eye, it looks like it's passing self twice! Returning > um.__a works exactly the same as self.__a! It is passing self twice, because you are using a bound method as the property method rather than an unbound method. > > I'm getting the feelin I may need to venture into comp.lang.Python > with this sort of stuff. > > Interesting. > > Liam Clarke > > On 9/25/05, Liam Clarke <[EMAIL PROTECTED]> wrote: > >>Hi, >> >> >> >>>You might want to learn more about the whole property mechanism then. >>>property() is actually a bit of sugar over a deeper mechanism. Also there is >>>an interesting idiom for creating properties using @apply (in Python 2.4) - >>>look for Benji York's comment in this recipe: >>>http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/410698 >> >>Thanks Kent. Just looking at that above recipe, I'm not too sure how >>the @ decorators work. >>From what I understand, it defines would turn apply() into a function >>that returns the various get/sets? >> >>Also found something interesting with property(), if it's called in >>__init__ you get >> >a.a >> >> >> >>whereas called outside __init__ it works normally. >> >>This is a hassle for me because I'm a lazy typist, so I've been using >>setattr() to pull attribute names out of a list. And the first >>argument setattr() requires is an object, and self doesn't work >>outside of a method, and using the class name leads to no attribute >>being set. >> >>Hmm, may have to learn even more about classes and their internals. >> >>Regards, >> >>Liam Clarke >> > > ___ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor > > ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] creating strings
Hello
How would I get the following program to accept inputs of exam scores from 0-100 with A being 100-90, B being 89-80, C being 79-70, D being 69-60, and F being everything less than 60?
import string
def main():
scores = ["F", "D", "C", "B", "A"]
g = input("Enter a score number (0-100): ")
print "The score of your exam is", scores [g-0] + "."
main()
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Re: [Tutor] (no subject)
I'd also like to mention that input() is bad, as you can enter Python
statements and it'll execute them. For instance, entering "sys.exit()"
would cause your programme to try and call sys.exit(), which if the
sys module had been imported, would quit.
You can do far more malevolent things than that, of course.
Best to use
g = int(raw_input("Enter a score number (0-100): "))
Come Python 3.0, raw_input and input are to both get the boot, I
believe, in favour of sys.stdin.read()
On 9/25/05, bob <[EMAIL PROTECTED]> wrote:
> At 03:29 PM 9/24/2005, [EMAIL PROTECTED] wrote:
>
> Hello
>
> How would I get the following program to accept inputs of exam scores from
> 0-100 with A being 100-90, B being 89-80, C being 79-70, D being 69-60, and
> F being everything less than 60?
> Many solutions are available. One could use an if statement:
>
> if g >= 90: s = 'A'
> elif g >= 80: s = 'B'
> ...
> else: g = 'F'
>
> although that can be hard to maintain.
>
> Or associate the lower limit with the data and search using a loop:
>
> scores = [("A",90), ("B",80), ("C".70), ("D",60),("F",0) ]
> for letter, number in scores:
> if g >= number:break
> print "The score of your exam is", letter
>
> This separates the data from the program structure and becomes much easier
> to maintain / extend, apply to new situation.
>
> If you are using a database then you could store these value pairs in a
> table and use SQL to retrieve the desired letter.
>
> When the number ranges have a nice progression, you can reduce the number
> to an index:
>
> print "The score of your exam is", "FEDCBAA"[g/10] # this is simpler
> code but harder to read/maintain.
>
> Or - knowing that chr(65) = "A", chr(66) = "B" you could convert the number
> to be in the range 65..70 and use chr()
>
>
> import string
> You do not refer to the string module, so there is no need to import it.
> Also be ware that it will eventually go away.
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>
>
>
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[Tutor] numbers from a name
Hello
with the following program I would like it to be able to take a person's name and then assign values to each letter and come up with a sum of all the letters in the name. for example if I entered bob. i would like the program to be able to print bob and then print the total of bob which would be 2 + 15 + 2 = 18.
import string
def main():
value = (raw_input("Please enter your first name"))
table = {'a' : 1, 'b' : 2, 'c' : 3, 'd' : 4, 'e' : 5, 'f' : 6, 'g' : 7, 'h' : 8, 'i' : 9, 'j' : 10, 'k' : 11, 'l' : 12, 'm' : 13, 'n' : 14, 'o' : 15, 'p' : 16, 'q' : 17, 'r' : 18, 's' : 19, 't' : 20, 'u' : 21, 'v' : 22, 'w' : 23, 'x' : 24, 'y' : 25, 'z' : 26}
total = 0
name = list(name)
for string in name:
total += table[string.lower()]
print "The total of your name is:", total
main()
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Re: [Tutor] numbers from a name
On Sat, 2005-09-24 at 23:50 -0400, [EMAIL PROTECTED] wrote:
> Hello
Hi Goofball...
>
> with the following program I would like it to be able to take a
> person's name and then assign values to each letter and come up with
> a sum of all the letters in the name. for example if I entered bob. i
> would like the program to be able to print bob and then print the
> total of bob which would be 2 + 15 + 2 = 18.
>
It should be 19, not 18.
> import string
You don't need the "string" module for something this simple. Just
read.
> def main():
>value = (raw_input("Please enter your first name"))
Why the parenthesis? This is better:
value = raw_input("Please enter your first name: ")
Also, after that you can convert the whole string to lower letters in
one step:
value = value.lower()
A good resource for information about Python's built-ins and modules is
to start the Python shell and type "help(something)", where "something"
is what you want more info about.
In the above example, "raw_input" will return an object of type "str".
Type "help(str)" and see a lot of things you could do to/with "str"
objects! (By the way, I found that "raw_input" returns "str" by typing
"help(raw_input) in Python! :) )
> table = {'a' : 1, 'b' : 2, 'c' : 3, 'd' : 4, 'e' : 5, 'f' : 6,
> 'g' : 7, 'h' : 8, 'i' : 9, 'j' : 10, 'k' : 11, 'l' : 12, 'm' : 13,
> 'n' : 14, 'o' : 15, 'p' : 16, 'q' : 17, 'r' : 18, 's' : 19, 't' : 20,
> 'u' : 21, 'v' : 22, 'w' : 23, 'x' : 24, 'y' : 25, 'z' : 26}
You could write a loop to create the "table" for you. Though, It will
be slower than the above method and will consume more system resources.
But it will be much easier on you. (A Real Programmer is a lazy one!:)
Just kidding!)
>
> total = 0
> name = list(name)
What's "name" for? Also, "name" never used before! Did you mean
"name=list(value)"? But I don't see how's that going to help.
>
> for string in name:
> total += table[string.lower()]
> print "The total of your name is:", total
"string" is the name of a module! You can't use it here _if_ you
imported that module. And as mentioned above, what's "name"?
Try this:
for x in value:
total += table[x]
print "The total of your name is:", total
"x" will iterate for each item (in this case, letter) in "value" which
holds the lowered case input. "table" have each letter assigned to a
number. "table[x]" will look-up "table" and _return_ the _number_
assigned to the letter that is held in "x".
If you didn't understand this just ask here again and many well be glad
to help.
> main()
Ziyad.
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Re: [Tutor] numbers from a name
How could I change the program to accept something like: John Bob Zelle Python or Kip Rada? ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] printing an acronym
On Sat, 24 Sep 2005 [EMAIL PROTECTED] wrote: > How could I get the following to print out an acronym for each phrase > entered such as if I entered random access memory it word print out RAM? Hello, Just out of curiosity, are you already familiar with Python's "lists"? If so, then you might want to try the slightly easier problem of pulling out acronyms out of a list of words. Extracting an acronym out of a list like: ["International", "Business", "Machines"] ==> "IBM" is not too bad, and is one step toward doing the original problem on the phrase "International Business Machines". Tutorials like: http://www.freenetpages.co.uk/hp/alan.gauld/tutseq2.htm and the other tutorials on: http://wiki.python.org/moin/BeginnersGuide/NonProgrammers should talk about lists. Please feel free to ask questions here! ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] (no subject)
On Sat, 24 Sep 2005 [EMAIL PROTECTED] wrote: > How would I get the following program to accept inputs of exam scores > from 0-100 with A being 100-90, B being 89-80, C being 79-70, D being > 69-60, and F being everything less than 60? Hello, Are you familiar with "if/elif/else"? These "control-flow" statements should help you express the above grading idea fairly straightforwardly. For experienced programmers, there is a module in the Standard Library that does pretty much what you want. I'll link to it below, but you probably won't want to use it: learn to use if/elif/else first; I'd hate to stunt your Python learning. *grin* Link for experienced programmers: http://www.python.org/doc/lib/bisect-example.html ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
