Re: [Tutor] Why do I not get the same results for these two functions when I pass 7 as an argument?
On 03/05/2013 07:10, Nonso Ibenegbu wrote:
Hello everyone,
Wonder if someone can help me understand why these two codes do not give
the same results for what looks essentially the same ("?") code. The
argument passed is
7.
def rental_car_cost(days):
payment = days * 40
if days >= 7:
return payment - 50
elif days >= 3 < 7:
return payment - 20
else:
return payment
and...
def rental_car_cost(days):
payment = days * 40
if days >= 3 < 7:
return payment - 20
elif days >= 7:
return payment - 50
else:
return payment
Python comparisons are chained. days >= 3 < 7 is saying "days is
greater or equal to 3 and 3 is less than 7". You need 3 <= days < 7.
--
If you're using GoogleCrap™ please read this
http://wiki.python.org/moin/GoogleGroupsPython.
Mark Lawrence
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Re: [Tutor] query from sqlalchemy returns AttributeError: 'NoneType' object
On 02/05/13 23:13, Karthik Sharma wrote: This doesn't have much to do with learning Python and a lot to do with SqlAlchemy so you'd be better off asking on a SqlAlchemy forum I suspect. However, some basic debugging investigation first may help your cause. For example... Traceback (most recent call last): ... File "/home/karthik/pox/tutorial.py", line 118, in _handle_PacketIn self.act_like_switch(packet, packet_in) File "/home/karthik/pox/tutorial.py", line 86, in act_like_switch self.send_packet(packet_in.buffer_id, packet_in.data,q_res.port_no, packet_in.in_port) AttributeError: 'NoneType' object has no attribute 'port_no' Have you checked to see what q_res is supposed to be? And where it comes from? And why it's apparently a NoneType? Some print statements might be in order? That will help anyone who can help you to so do. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Why do I not get the same results for these two functions when I pass 7 as an argument?
You need to change the condition statement:
if days >= 3 < 7: to thisif days >= 3 and days < 7:
When it goes through the function it sees this statement days >= 3 as true and
execute - payment -20.
Askar
From: Nonso Ibenegbu [mailto:jollyn...@gmail.com]
Sent: Friday, May 03, 2013 2:10 AM
To: Tutor@python.org
Subject: [Tutor] Why do I not get the same results for these two functions when
I pass 7 as an argument?
Hello everyone,
Wonder if someone can help me understand why these two codes do not give the
same results for what looks essentially the same ("?") code. The argument
passed is
7.
def rental_car_cost(days):
payment = days * 40
if days >= 7:
return payment - 50
elif days >= 3 < 7:
return payment - 20
else:
return payment
and...
def rental_car_cost(days):
payment = days * 40
if days >= 3 < 7:
return payment - 20
elif days >= 7:
return payment - 50
else:
return payment
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Re: [Tutor] Why do I not get the same results for these two functions when I pass 7 as an argument?
Great! Many thanks for the help offered. The background of the problem is
that if I book a certain service for 1 or 2 days I pay $40 per day, if I
book 3, 4, 5 or 6 days I get $20 off but if I book above 7 days I get $50
off.
The first function does the job!
The second function breaks down when the argument is 7 or above.
Yet the only difference is that the condition "if days >= 7:" comes first
in the first function but comes second (as "elif days >= 7:") in the second
code.
I think essentially that the difference lies in the fact that the
conditions were swapped. But how are they different?
On Fri, May 3, 2013 at 8:07 AM, Mark Lawrence wrote:
> On 03/05/2013 07:10, Nonso Ibenegbu wrote:
>
>> Hello everyone,
>> Wonder if someone can help me understand why these two codes do not give
>> the same results for what looks essentially the same ("?") code. The
>> argument passed is
>> 7.
>>
>> def rental_car_cost(days):
>> payment = days * 40
>> if days >= 7:
>> return payment - 50
>> elif days >= 3 < 7:
>> return payment - 20
>> else:
>> return payment
>>
>> and...
>>
>> def rental_car_cost(days):
>> payment = days * 40
>> if days >= 3 < 7:
>> return payment - 20
>> elif days >= 7:
>> return payment - 50
>> else:
>> return payment
>>
>>
> Python comparisons are chained. days >= 3 < 7 is saying "days is greater
> or equal to 3 and 3 is less than 7". You need 3 <= days < 7.
>
> --
> If you're using GoogleCrap™ please read this http://wiki.python.org/moin/*
> *GoogleGroupsPython .
>
> Mark Lawrence
>
> __**_
> Tutor maillist - Tutor@python.org
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>
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Re: [Tutor] Why do I not get the same results for these two functions when I pass 7 as an argument?
On 03/05/13 17:51, Nonso Ibenegbu wrote: The second function breaks down when the argument is 7 or above. Yet the only difference is that the condition "if days >= 7:" comes first in the first function but comes second (as "elif days >= 7:") in the second code. Yes but that's because the other expression is nonsense (to python). You cannot write if days >= 3 < 7: It doesn't make any sense. What you mean is if days >=3 and days < 7 If you fix that then the two functions will have similar logic. In Python 9unlike most languages) you can abbreviate that but not the way you did it. You need to use if 3 <= days < 7: Note that the variable is in the middle and the test for 3 is now reversed (3<=days). If in doubt use the double test combined by 'and' as above. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Why do I not get the same results for these two functions when I pass 7 as an argument?
> elif days >= 3 < 7: This condition here, as well as: > if days >= 3 < 7: this condition here, looks very suspicious. Can you say what you trying to express here? ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] creating a corpus from a csv file
Hi,
I'm very new to python and am trying to figure out how to make a corpus from a
text file. I have a csv file (actually pipe '|' delimited) where each row
corresponds to a different text document. Each row contains a communication
note. Other columns correspond to categories of types of communications. I am
able to read the csv file and print the notes column as follows:
import csv
with open('notes.txt', 'rb') as infile:
reader = csv.reader(infile, delimiter = '|')
i = 0
for row in reader:
if i <= 25: print row[8]
i = i+1
I would like to convert this to a categorized corpus with some of the other
columns corresponding to the categories. All of the columns are text (i.e.,
strings). I have looked for documentation on how to use csv.reader with
PlaintextCorpusReader but have been unsuccessful in finding a example similar
to what I want to do. Can someone please help?
Thanks,
Bob
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Re: [Tutor] creating a corpus from a csv file
On 03/05/13 21:48, Treder, Robert wrote:
I'm very new to python and am trying to figure out how to
> make a corpus from a text file.
Hi, I for one have no idea what a corpus is or looks like
so you will need to help us out a little before we can help you.
I have a csv file (actually pipe '|' delimited) where each
row corresponds to a different text document.
Each row contains a communication note.
> Other columns correspond to categories of types of communications.
I am able to read the csv file and print the notes column as follows:
import csv
with open('notes.txt', 'rb') as infile:
reader = csv.reader(infile, delimiter = '|')
i = 0
for row in reader:
if i <= 25: print row[8]
i = i+1
You don't need to manually manage 'i'.
you could do this instead:
with open('notes.txt', 'rb') as infile:
reader = csv.reader(infile, delimiter = '|')
for count, row in enumerate(reader):
if count <= 25: print row[8] # I assume indented?
else: break # save time if its a big file
I would like to convert this to a categorized corpus with
> some of the other columns corresponding to the categories.
You might be able to use a dictionary but for now
I'm still not clear what you mean. Can you show us
some sample input and output data?
> documentation on how to use csv.reader with PlaintextCorpusReader
never heard of the latter - is it an external module?
HTH
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
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Re: [Tutor] Why do I not get the same results for these two functions when I pass 7 as an argument?
On 05/03/2013 12:51 PM, Nonso Ibenegbu wrote: Great! Many thanks for the help offered. The background of the problem is that if I book a certain service for 1 or 2 days I pay $40 per day, if I book 3, 4, 5 or 6 days I get $20 off but if I book above 7 days I get $50 off. The first function does the job! By accident only. The elif on the first one doesn't compare days to 7 at all. So it's simply equivalent to: elif days >= 3: If you can't understand that, then comparing the two functions is useless. -- DaveA ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] changing char list to int list isn't working
I'm turning an integer into a string so I can make a list of separate chars, then turn those chars back into individual ints, but the resulting list still looks like string chars when I print it. What am I doing wrong? listOfNumChars = list(str(intNum)) for num in listOfNumChars: num = int(num) print(listOfNumChars) # result of 455 entered is ['4', '5', '5'] -- Jim Mooney “For anything that matters, the timing is never quite right, the resources are always a little short, and the people who affect the outcome are always ambivalent.” ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] changing char list to int list isn't working
On Sat, May 4, 2013 at 12:13 AM, Jim Mooney wrote: > I'm turning an integer into a string so I can make a list of separate > chars, then turn those chars back into individual ints, but the > resulting list still looks like string chars when I print it. What am > I doing wrong? > > listOfNumChars = list(str(intNum)) > for num in listOfNumChars: > num = int(num) > > print(listOfNumChars) > > # result of 455 entered is ['4', '5', '5'] The body of your for loop only rebinds the loop variable. It's not appending to a new list or modifying listOfNumChars. As to the latter list, it's redundant since a string is iterable. The following snippet creates the list [4, 5, 5]: num = 455 numlist = [] for c in str(num): numlist.append(int(c)) or using a list comprehension: numlist = [int(c) for c in str(num)] or using map: numlist = list(map(int, str(num))) iterators http://docs.python.org/3/library/stdtypes.html#typeiter built-in functions http://docs.python.org/3/library/functions.html#iter http://docs.python.org/3/library/functions.html#map for statement http://docs.python.org/3/reference/compound_stmts.html#the-for-statement comprehensions http://docs.python.org/3/reference/expressions.html#displays-for-lists-sets-and-dictionaries ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] changing char list to int list isn't working
On 04/05/13 14:13, Jim Mooney wrote:
I'm turning an integer into a string so I can make a list of separate
chars, then turn those chars back into individual ints, but the
resulting list still looks like string chars when I print it. What am
I doing wrong?
listOfNumChars = list(str(intNum))
This creates a list of characters.
for num in listOfNumChars:
num = int(num)
This walks over the list, setting the variable "num" to each character in turn, then inside
the loop you set the variable "num" to the converted char->int. But num isn't linked to
the list in any way -- num has no memory that the value it got came from a list. Reassigning num
inside the loop doesn't touch the list in any way, so naturally the list doesn't change.
print(listOfNumChars)
# result of 455 entered is ['4', '5', '5']
To split a number into digits, the shortest way is to use a list comprehension:
digits = [int(c) for c in str(num)]
We can expand that list comp into a for-loop:
digits = []
for c in str(num):
digits.append(int(c))
Notice that there is no need to convert the string into a list. You can iterate
over the characters of a string just fine.
If you prefer to create a list, then modify it in place, we can do this:
digits = list(str(num))
for position, char in enumerate(digits):
digits[position] = int(char)
Here we use enumerate() to iterate over pairs of (position, value) instead of
just value:
py> list("abcd")
['a', 'b', 'c', 'd']
py> list(enumerate("abcd"))
[(0, 'a'), (1, 'b'), (2, 'c'), (3, 'd')]
Here's another way, using map:
digits = map(int, str(num)) # Python 2.x only
digits = list(map(int, str(num))) # Python 3.x or better
Why the difference between Python 2.x and 3.x? In 2.x, map is "eager", it runs all the
way through the string as soon as you call it, returning a list. In 3.x, map is "lazy",
and only generates values when and as needed. By wrapping the map generator in a call to list, that
forces it to run all the way through the string.
--
Steven
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