Re: [Tutor] text files
On 16/01/13 02:31, Gina wrote:
new_file = open("the_file_upper.txt", "w+")
In general consider the w+ file option to be for advanced use only.
Either open it for reading or writing, don't try to do both at the same
time. It's a bit like sitting on a tree branch with a saw to cut it
down. If you cut on the wrong side you get hurt...
new_file.write(*)
print(new_file.read())
This won't read anything because the file cursor is at the end of the
string that you wrote (remember the branch illustration?)
new_file.close()
And this just closes the file with a short line of asterisks in it...
Not really what you want.
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
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Re: [Tutor] Question regarding lists and manipulating items in lists.
On 16/01/13 11:23, Scurvy Scott wrote: After playing with your example I keep being told that list has no attribute int_to_note. I know what the problem is, I just don't know how to fix it. Oops, sorry about that, that is my fault. I did warn that my code was untested! If you know what the problem is, the solution should be obvious. Before reading ahead, try explaining to yourself what you think the problem actually is. If you do that, the answer should pop right out at you. Still need a hint? Okay, try this: "I need to convert the Fibonacci integers to musical notes, using the notes.int_to_note function imported from mingus.core. But inside Steven's make_notes function, he sets a local variable `notes = []`, which means that inside the function I cannot access the global notes.int_to_note." Or, a shorter version: "I have notes.int_to_note, which I need, but accessing it is blocked by the local variable notes which is a list." So the obvious solution is... ...rename the local variable `notes` to something else. def make_notes(num_notes): it = fib() music = [] # start with an empty list for i in range(num_notes): n = next(it) % 12 # get the next Fibonacci number, modulo 12 music.append(notes.int_to_note(n)) return music Still untested. Also, I believe I've fixed my email so it will no longer be in HTML or anything fancy, just plain text. Many thanks! More comments below. So right now my code is: import mingus.core.notes as notes #fibonacci def fib(): a, b = 0, 1 while True: yield b a, b = b, a+b I have now tested that, and it works fine: py> it = fib() py> [next(it) for i in range(15)] [1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610] Some people prefer to start the Fibonacci sequence with 0. That's an easy change to make: change the line "yield b" to "yield a". But Wolfram Mathworld and Mathematica start the Fibonacci sequence with 1, 1, 2, ... rather than 0, 1, 1, ... so that's good enough for me. http://mathworld.wolfram.com/FibonacciNumber.html def make_notes(num_notes): it = fib() notes = [] for i in range(num_notes): n = next(it) % 12 notes.append(notes.int_to_note(n)) return notes Which is pretty different from what my original code was. Maybe so, but I'm teaching you a practice that will see you in good stead whenever you program: each function should do *one* thing. Think of programming as creating tools. You wouldn't try to create a single tool for cutting wood, driving screws into it, and painting it. Instead we have three tools: saw, screwdriver, paint brush. It's *much* easier to make three separate tools than a single tool that tries to do all three jobs. Likewise for your program. It is better to write separate functions to: * create the Fibonacci numbers; * turn them into musical notes; than to do both jobs in one function. Now in *this* case, the labour saved is relatively small. But it is a good habit to get into, and when you get to large, complex programs it becomes essential. The generator function doesn't actually do anything when called, it just tells me it's a generator function and where it's located. If you look at how my code uses the generator function, you will see the correct way to use it. Here's another example: py> it = fib() py> n = next(it) py> while n < 100: ... print n ... n = next(it) ... 1 1 2 3 5 8 13 21 34 55 89 -- Steven ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Set LD_LIBRARY_PATH and equivalents platform-independently
Hello,
Is there a builtin function that can set LD_LIBRARY_PATH or equivalents
platform-independently? It would be nice use such a function in a setup script.
The code below illustrates what I mean, although it's entirely untested.
import sys
import os
def setPath(loc):
"""Set LD_LIBRARY_PATH and equivalents platform-independently"""
p = {"win": "PATH",
"lin": "LD_LIBRARY_PATH",
"solaris": "LD_LIBRARY_PATH",
"aix": "LIBPATH",
"darwin":
"DYLD_LIBRARY_PATH",
"hpux": "SHLIB_PATH"}
pf = sys.platform()
sep = ";" if pf.startswith("win") else ":"
try:
os.environ[p[pf]] += (sep + loc)
except KeyError:
print "Platform %s not supported" % pf
Regards,
Albert-Jan
~~
All right, but apart from the sanitation, the medicine, education, wine, public
order, irrigation, roads, a
fresh water system, and public health, what have the Romans ever done for
us?
~~ ___
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[Tutor] how to track an entry in a large text file
Say I have a text file (example below) that has multiple records with the same format but not always the same number of lines. Each record is separated by the line that starts with “Examining file” as in below example. If you notice, the 3D Val is not there for the second record. How do I report that the “3D Val” is not present for that particular record “8866W2310089.txt”? Thanks to Alan for his reply. Examining file: 5521W231.txt Duration : 0h : 59m First meas : week : 86 : 1721 Last meas : week : 89 : 1721 Min val : 15 Max val : 18 3D : 3600 100.0% summary Total MissedRate epoch1:1378 0 0\1000 epoch2:2154 1 0\1000 Examining file: 8866W2310089.txt Duration : 0h : 59m First meas : week : 87 : 1721 Last meas : week : 84 : 1721 Min val : 16 Max val : 19 summary Total MissedRate epoch1:1378 0 0\1000 epoch ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Json encode and decode on Puython 2.4
Dotan Cohen wrote: > > Hi all, I'm just getting into porting some PHP scripts to Python. One > issue that I'm having is that the scripts need to run on a host with > Python 2.4 that has neither the json nor simplejson packages > available. I figure that I'll have to include the loads() and dumps() > functions in my application. Where might I find the source for these > two functions? What would be the best way to include them? > > Thanks. > > -- > Dotan Cohen Python 2.4 is quite old and simplejson supports 2.5+. I can see a yield in the encoder code, so it is unlikely to be easy to modify and get working with 2.4. According to a stack overflow question you may want to look at older releases (example: 2.0.9/2.1) as being more 2.4 compatible. SimpleJson source: https://github.com/simplejson/simplejson Change the version in the link to see if PyPi has a different version. http://pypi.python.org/pypi/simplejson/2.1.0 I have no idea if you can get the json library to work with 2.4. I did not seen anything in my cursory glance that suggested it would not. http://hg.python.org/cpython-fullhistory/file/8e0b617c6c22/Lib/json/ You may want to see if you can get a newer python installed on the machine. You probably want it alt-installed so you are not replacing the system expected Python. ~Ramit This email is confidential and subject to important disclaimers and conditions including on offers for the purchase or sale of securities, accuracy and completeness of information, viruses, confidentiality, legal privilege, and legal entity disclaimers, available at http://www.jpmorgan.com/pages/disclosures/email. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] learning to program in cython
Hi Guys With the help of an awesome python community I have been able to pick up the language and now willing to explore other cool extensions of it. I routinely have large loops which could be ported to cython for speed. However I have never written a single line of cython code. Any pointers on getting started. A tutorial text or video would be of great help. Thanks! -Abhi ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Json encode and decode on Puython 2.4
On Wed, Jan 16, 2013 at 11:50 PM, Prasad, Ramit wrote: > Python 2.4 is quite old and simplejson supports 2.5+. I can see a > yield in the encoder code, so it is unlikely to be easy to modify > and get working with 2.4. According to a stack overflow question > you may want to look at older releases (example: 2.0.9/2.1) as being > more 2.4 compatible. > SimpleJson source: https://github.com/simplejson/simplejson > Change the version in the link to see if PyPi has a different version. > http://pypi.python.org/pypi/simplejson/2.1.0 > > I have no idea if you can get the json library to work with 2.4. > I did not seen anything in my cursory glance that suggested it would > not. > http://hg.python.org/cpython-fullhistory/file/8e0b617c6c22/Lib/json/ > > You may want to see if you can get a newer python installed on > the machine. You probably want it alt-installed so you are not > replacing the system expected Python. > > Thanks, Ramit. I'm now trying to install an older simplejson with simple_install by defining the install directory since I don't have root on this machine. Unfortunately, installing a newer Python (or anything else needed by root) is not going to happen on this particular webhost. Thanks. -- Dotan Cohen http://gibberish.co.il http://what-is-what.com ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] learning to program in cython
On 16 January 2013 21:54, Abhishek Pratap wrote: > Hi Guys > > With the help of an awesome python community I have been able to pick up the > language and now willing to explore other cool extensions of it. Good work! > > I routinely have large loops which could be ported to cython for speed. > However I have never written a single line of cython code. Any pointers on > getting started. There are two reasons for using cython: 1) To interface directly with existing C libraries. 2) To speed up CPU-intensive code. It sounds like you're interested in case 2). However, not all loops benefit from cythonisation. Loosely cython is good when a) you're doing something that can be written in a small amount of efficient C code b) but the corresponding Python code involves a lot of repeated function calls or expression evaluations. If you're already familiar with C then you'll probably have some idea when a) and b) apply. I would say that a prerequisite for learning to speed up CPU-intensive code with cython would be learning to use the python profilers. In particular you should learn to use cProfile and timeit: http://docs.python.org/2/library/profile.html http://docs.python.org/2/library/timeit.html As with any optimisation it is important to study the performance of your code and identify bottlenecks first. It is also generally true that you should (at least) consider algorithmic optimisation before you consider using something like cython for micro-optimisation. One of the guiding principles in the design of the Python language is that big-O complexity is often more important than micro-optimisation. Similarly, you should normally try to optimise and benchmark your code in pure Python before attempting to improve on that with cython. > > A tutorial text or video would be of great help. Here is the official "basic tutorial" for cython: http://docs.cython.org/src/userguide/tutorial.html There are also lots of helpful people on the cython-users mailing list: https://groups.google.com/forum/?fromgroups#!forum/cython-users If you have a particular problem in mind that might benefit from cythonisation, then why not post (a shortened but complete version of) it here to see if anyone has any pointers about how to improve the performance with/without cython. Oscar ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] how to track an entry in a large text file
On 16 January 2013 21:22, 3n2 Solutions <3n2soluti...@gmail.com> wrote:
> Say I have a text file (example below) that has multiple records with
> the same format but not always the same number of lines. Each record
> is separated by the line that starts with “Examining file” as in below
> example. If you notice, the 3D Val is not there for the second record.
> How do I report that the “3D Val” is not present for that particular
> record “8866W2310089.txt”?
> Thanks to Alan for his reply.
I don't follow what you mean by 'How do I report that the “3D Val” is
not present for that particular
record “8866W2310089.txt”?'
The obvious answer would be (assuming the filename is currently set to
“8866W2310089.txt”):
print('3D Val not present in %s' % filename)
I wonder if your actual question is:
1) How do I detect that it is not present? - check for a line starting
with '3D' while reading the file.
2) How do I mark it is not being present in my data structure? -
depends what kind of data structure you are using. A common idiom
would be to simply use the value None as a place-holder for situations
where the value is not supplied.
3) Something else...
>
> Examining file: 5521W231.txt
>
> Duration : 0h : 59m
> First meas : week : 86 : 1721
> Last meas : week : 89 : 1721
>
> Min val : 15
> Max val : 18
> 3D : 3600 100.0%
>
> summary Total MissedRate
> epoch1:1378 0 0\1000
> epoch2:2154 1 0\1000
>
>
>
> Examining file: 8866W2310089.txt
>
> Duration : 0h : 59m
> First meas : week : 87 : 1721
> Last meas : week : 84 : 1721
>
> Min val : 16
> Max val : 19
>
> summary Total MissedRate
> epoch1:1378 0 0\1000
> epoch
Oscar
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Re: [Tutor] Json encode and decode on Puython 2.4
On 17/01/13 08:50, Prasad, Ramit wrote: Python 2.4 is quite old and simplejson supports 2.5+. I can see a yield in the encoder code, so it is unlikely to be easy to modify and get working with 2.4. Python 2.4 supports yield. -- Steven ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Json encode and decode on Puython 2.4
On 17/01/13 08:15, Dotan Cohen wrote: Hi all, I'm just getting into porting some PHP scripts to Python. One issue that I'm having is that the scripts need to run on a host with Python 2.4 that has neither the json nor simplejson packages available. I figure that I'll have to include the loads() and dumps() functions in my application. Where might I find the source for these two functions? What would be the best way to include them? Python 2.4 is no longer receiving security updates. If you're exposing a web app on the Internet using Python 2.4, it's just a matter of time before you're hacked. Time to change hosting companies, methinks. If it is a Centos or RedHat based Linux system, it will support simplejson. [steve@ando /]$ sudo yum install simplejson [sudo] password for steve: [...extremely long output deleted...] Installed: python-simplejson.i386 0:2.0.9-8.el5 Complete! [steve@ando /]$ python2.4 Python 2.4.3 (#1, Jun 18 2012, 08:55:31) [GCC 4.1.2 20080704 (Red Hat 4.1.2-52)] on linux2 Type "help", "copyright", "credits" or "license" for more information. py> import simplejson py> print simplejson -- Steven ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Json encode and decode on Puython 2.4
Steven D'Aprano wrote: > > On 17/01/13 08:50, Prasad, Ramit wrote: > > > Python 2.4 is quite old and simplejson supports 2.5+. I can see a > > yield in the encoder code, so it is unlikely to be easy to modify > > and get working with 2.4. > > Python 2.4 supports yield. Thanks for the correction; I did not realize it was added in 2.2/2.3. Ramit This email is confidential and subject to important disclaimers and conditions including on offers for the purchase or sale of securities, accuracy and completeness of information, viruses, confidentiality, legal privilege, and legal entity disclaimers, available at http://www.jpmorgan.com/pages/disclosures/email. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] how to track an entry in a large text file
On 01/16/2013 04:22 PM, 3n2 Solutions wrote: Say I have a text file (example below) that has multiple records with the same format but not always the same number of lines. Each record is separated by the line that starts with “Examining file” as in below example. If you notice, the 3D Val is not there for the second record. How do I report that the “3D Val” is not present for that particular record “8866W2310089.txt”? Thanks to Alan for his reply. Examining file: 5521W231.txt Duration : 0h : 59m First meas : week : 86 : 1721 Last meas : week : 89 : 1721 Min val : 15 Max val : 18 3D : 3600 100.0% summary Total MissedRate epoch1:1378 0 0\1000 epoch2:2154 1 0\1000 Examining file: 8866W2310089.txt Duration : 0h : 59m First meas : week : 87 : 1721 Last meas : week : 84 : 1721 Min val : 16 Max val : 19 summary Total MissedRate epoch1:1378 0 0\1000 epoch ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor If the file isn't very huge, you can split by "Examining file: ", then iterate over the list, check if '3D' is in the item; if it isn't, split the item by newlines and print first line. HTH, - mitya -- Lark's Tongue Guide to Python: http://lightbird.net/larks/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Set LD_LIBRARY_PATH and equivalents platform-independently
On 16/01/13 21:06, Albert-Jan Roskam wrote: Is there a builtin function that can set LD_LIBRARY_PATH or equivalents platform-independently? No. But there is putenv() in the os module. But how well it works across OS I'm not sure. HTH -- 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] Set LD_LIBRARY_PATH and equivalents platform-independently
On 01/16/2013 07:05 PM, Alan Gauld wrote: On 16/01/13 21:06, Albert-Jan Roskam wrote: Is there a builtin function that can set LD_LIBRARY_PATH or equivalents platform-independently? No. But there is putenv() in the os module. But how well it works across OS I'm not sure. I don't recall enough about Windows to be sure whether putenv would work, but the environment variable Windows uses to search for DLL's is certainly not LD_LIBRARY_PATH -- DaveA ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
