Tagged Questions

115
votes
6answers
3k views

What is […] in Python 2.7?

I was playing around in python. I used the following code in IDLE p = [1, 2] p[1:1] = [p] print p The output was [1, [...], 2] What is this […]? Interestingly I could now use this as a list of ...
88
votes
1answer
3k views

Why is early return slower than else?

This is a follow-up question to an answer I gave a few days back. Edit: it seems that the OP of that question already used the code I posted to him to ask the same question, but I was unaware of it. ...
77
votes
2answers
2k views

str performance in python

While profiling a piece of python code (python 2.6 up to 3.2), I discovered that the str method to convert an object (in my case an integer) to a string is almost an order of magnitude slower than ...
65
votes
1answer
2k views

Python: why are * and ** faster than / and sqrt()?

While optimising my code I realised the following: >>> from timeit import Timer as T >>> T(lambda : 1234567890 / 4.0).repeat() [0.22256922721862793, 0.20560789108276367, ...
43
votes
3answers
41k views

How to uninstall Python 2.7 on a Mac OS X 10.6.4?

I want to completely remove Python 2.7 from my Mac OS X 10.6.4. I managed to remove the entry from the PATH variable by reverting my .bash_profile. But I also want to remove all directories, files, ...
29
votes
5answers
3k views

Python: What's the difference between __builtin__ and __builtins__?

I was coding today and noticed something. If I open a new interpreter session (IDLE) and check what's defined with the dir function I get this: $ python >>> dir() ['__builtins__', '__doc__', ...
23
votes
4answers
9k views

Why is parenthesis in print voluntary in Python 2.7?

In Python 2.7 both the following will do the same print("Hello, world!") # Prints "Hello, world!" print "Hello, world!" # Prints "Hello, world!" However the following will not print("Hello,", ...
22
votes
4answers
3k views

What is the cross-platform method of enumerating serial ports in Python (including virtual ports)?

Note: I'm using Python 2.7, and pySerial for serial communications. I found this article which lists two ways: http://www.zaber.com/wiki/Software/Python#Displaying_a_list_of_available_serial_ports ...
21
votes
3answers
992 views

Python — what is NOT in 2.7 that IS in 3.1? So many things have been back-ported, what is NOT?

I've been following the saga of Python 3.x and have watched the 3.x features gradually getting back-ported to the 2.x line. Most of the libraries I use haven't been ported and some (e.g. Twisted) ...
19
votes
2answers
135 views

Why are these two functions different?

Take a look at this: >>> def f(): ... return (2+3)*4 ... >>> dis(f) 2 0 LOAD_CONST 5 (20) 3 RETURN_VALUE Evidently, the compiler has ...
18
votes
2answers
24k views

Installing Numpy on 64bit Windows 7 with Python 2.7.3

It looks like the only 64 bit windows installer for Numpy is for Numpy version 1.3.0 which only works with Python 2.6 http://sourceforge.net/projects/numpy/files/NumPy/ It strikes me as strange that ...
18
votes
7answers
473 views

Constructing the largest number possible by rearranging a list

Say I have an array of positive whole integers; I'd like to manipulate the order so that the concatenation of the resultant array is the largest number possible. For example [97, 9, 13] results in ...
18
votes
1answer
515 views

Huge memory leak in repeated os.path.isdir calls?

I've been scripting something that has to do with scanning directories and noticed a severe memory leak when calling os.path.isdir, so I've tried the following snippet: def func(): if not ...
1
vote
1answer
45 views

Numpy reshape yields a different size error

I have a piece of Python code which has been used for about a year without any issues (it reads, uncompresses/unpacks data, selects a window and plots it using Numpy/Matplotplib). We recently got a ...
0
votes
2answers
32 views

Using an Environmental Variables In a Variety of Path Types

How would i go about using the same method for using the USERNAME variable in the top portion of code in the bottom code, i just feel like i don't have a grounded knowledge of the syntax with ...

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