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Installing Numpy on 64bit Windows 7 with Python 2.7.3 [closed]

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 I would have to roll back to Python 2.6 to use Numpy on Windows, which makes me think I'm missing something.

Am I?

How to convert a Python datetime object to seconds

Apologies for the simple question... I'm new to Python... I have searched around and nothing seems to be working.

I have a bunch of datetime objects and I want to calculate the number of seconds since a fixed time in the past for each one (for example since January 1, 1970).

import datetime
t = datetime.datetime(2009, 10, 21, 0, 0)

This seems to be only differentiating between dates that have different days:

t.toordinal()

Any help is much appreciated.

Why does "not(True) in [False, True]" return False?

If I do this:

>>> False in [False, True]
True

That returns True. Simply because False is in the list.

But if I do:

>>> not(True) in [False, True]
False

That returns False. Whereas not(True) is equal to False:

>>> not(True)
False

Why?

Python 2.7 on Ubuntu

I am new to Python and am working on a Linux machine (Ubuntu 10.10). It is running python 2.6, but I'd like to run 2.7 as it has features I want to use. I have been urged to not install 2.7 and set that as my default python.

My question is, how can I install 2.7 and run it side by side with 2.6?

python convert list to tuple

I'm trying to convert a list to a tuple. When I google it I find a lot of answers similar to:

l = [4,5,6]
tuple(l)

But if I do that I get this error message:

TypeError: 'tuple' object is not callable

How can I selectively escape percent (%) in Python strings?

I have the following code

test = "have it break."
selectiveEscape = "Print percent % in sentence and not %s" % test

print(selectiveEscape)

I would like to get the output:

Print percent % in sentence and not have it break.

What actually happens:

    selectiveEscape = "Use percent % in sentence and not %s" % test
TypeError: %d format: a number is required, not str

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 using string formatting.

Here is the benchmark

>>> from timeit import Timer
>>> Timer('str(100000)').timeit()
0.3145311339386332
>>> Timer('"%s"%100000').timeit()
0.03803517023435887

Does anyone know why this is the case? Am I missing something?

How to hide output of subprocess in Python 2.7

I'm using eSpeak on Ubuntu and have a Python 2.7 script that prints and speaks a message:

import subprocess
text = 'Hello World.'
print text
subprocess.call(['espeak', text])

eSpeak produces the desired sounds, but clutters the shell with some errors (ALSA lib..., no socket connect) so i cannot easily read what was printed earlier. Exit code is 0.

Unfortunately there is no documented option to turn off its verbosity, so I'm looking for a way to only visually silence it and keep the open shell clean for further interaction.

How can I do this?

Why are Python's 'private' methods not actually private?

Python gives us the ability to create 'private' methods and variables within a class by prepending double underscores to the name, like this: __myPrivateMethod(). How, then, can one explain this

>>> class MyClass:
...     def myPublicMethod(self):
...             print 'public method'
...     def __myPrivateMethod(self):
...             print 'this is private!!'
... 
>>> obj = MyClass()
>>> obj.myPublicMethod()
public method
>>> obj.__myPrivateMethod()
Traceback (most recent call last):
  File "", line 1, in 
AttributeError: MyClass instance has no attribute '__myPrivateMethod'
>>> dir(obj)
['_MyClass__myPrivateMethod', '__doc__', '__module__', 'myPublicMethod']
>>> obj._MyClass__myPrivateMethod()
this is private!!

What's the deal?!

I'll explain this a little for those who didn't quite get that.

>>> class MyClass:
...     def myPublicMethod(self):
...             print 'public method'
...     def __myPrivateMethod(self):
...             print 'this is private!!'
... 
>>> obj = MyClass()

What I did there is create a class with a public method and a private method and instantiate it.

Next, I call its public method.

>>> obj.myPublicMethod()
public method

Next, I try and call its private method.

>>> obj.__myPrivateMethod()
Traceback (most recent call last):
  File "", line 1, in 
AttributeError: MyClass instance has no attribute '__myPrivateMethod'

Everything looks good here; we're unable to call it. It is, in fact, 'private'. Well, actually it isn't. Running dir() on the object reveals a new magical method that python creates magically for all of your 'private' methods.

>>> dir(obj)
['_MyClass__myPrivateMethod', '__doc__', '__module__', 'myPublicMethod']

This new method's name is always an underscore, followed by the class name, followed by the method name.

>>> obj._MyClass__myPrivateMethod()
this is private!!

So much for encapsulation, eh?

In any case, I'd always heard Python doesn't support encapsulation, so why even try? What gives?

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. Apologies. The answers provided are different though!

Substantially I observed that:

>>> def without_else(param=False):
...     if param:
...         return 1
...     return 0
>>> def with_else(param=False):
...     if param:
...         return 1
...     else:
...         return 0
>>> from timeit import Timer as T
>>> T(lambda : without_else()).repeat()
[0.3011460304260254, 0.2866089344024658, 0.2871549129486084]
>>> T(lambda : with_else()).repeat()
[0.27536892890930176, 0.2693932056427002, 0.27011704444885254]
>>> T(lambda : without_else(True)).repeat()
[0.3383951187133789, 0.32756996154785156, 0.3279120922088623]
>>> T(lambda : with_else(True)).repeat()
[0.3305950164794922, 0.32186388969421387, 0.3209099769592285]

...or in other words: having the else clause is faster regardless of the if condition being triggered or not.

I assume it has to do with different bytecode generated by the two, but is anybody able to confirm/explain in detail?

EDIT: Seems not everybody is able to reproduce my timings, so I thought it might be useful to give some info on my system. I'm running Ubuntu 11.10 64 bit with the default python installed. python generates the following version information:

Python 2.7.2+ (default, Oct  4 2011, 20:06:09) 
[GCC 4.6.1] on linux2

Here are the results of the disassembly in Python 2.7:

>>> dis.dis(without_else)
  2           0 LOAD_FAST                0 (param)
              3 POP_JUMP_IF_FALSE       10

  3           6 LOAD_CONST               1 (1)
              9 RETURN_VALUE        

  4     >>   10 LOAD_CONST               2 (0)
             13 RETURN_VALUE        
>>> dis.dis(with_else)
  2           0 LOAD_FAST                0 (param)
              3 POP_JUMP_IF_FALSE       10

  3           6 LOAD_CONST               1 (1)
              9 RETURN_VALUE        

  5     >>   10 LOAD_CONST               2 (0)
             13 RETURN_VALUE        
             14 LOAD_CONST               0 (None)
             17 RETURN_VALUE        

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, symlinks, and entries that got installed by the Python 2.7 install package. I've got the install package from http://www.python.org/. What directories/files/configuration file entries do I need to remove? Is there a list somewhere?

pydot and graphviz error: Couldn't import dot_parser, loading of dot files will not be possible

When I run a very simple code with pydot

import pydot # import pydot or you're not going to get anywhere my friend :D 

graph = pydot.Dot(graph_type='graph')

for i in range(3):

  edge = pydot.Edge("king", "lord%d" % i)
  graph.add_edge(edge)

vassal_num = 0
for i in range(3):
  for j in range(2):
    edge = pydot.Edge("lord%d" % i, "vassal%d" % vassal_num)
    graph.add_edge(edge)
    vassal_num += 1

graph.write_png('example1_graph.png')

It prints me the error message:

Couldn't import dot_parser, loading of dot files will not be possible.

I'm using python 2.7.3

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, 0.20530295372009277]
>>> from __future__ import division
>>> T(lambda : 1234567890 / 4).repeat()
[0.14969301223754883, 0.14155197143554688, 0.14141488075256348]
>>> T(lambda : 1234567890 * 0.25).repeat()
[0.13619112968444824, 0.1281130313873291, 0.12830305099487305]

and also:

>>> from math import sqrt
>>> T(lambda : sqrt(1234567890)).repeat()
[0.2597470283508301, 0.2498021125793457, 0.24994492530822754]
>>> T(lambda : 1234567890 ** 0.5).repeat()
[0.15409398078918457, 0.14059877395629883, 0.14049601554870605]

I assume it has to do with the way python is implemented in C, but I wonder if anybody would care to explain why is so?

Delete a dictionary item if the key exists [duplicate]

Is there any other way to delete an item in a dictionary only if the given key exists, other than:

if key in mydict:
    del mydict[key]

The scenario is that I'm given a collection of keys to be removed from a given dictionary, but I am not certain if all of them exist in the dictionary. Just in case I miss a more efficient solution.

Installing PIL with pip

I am trying to install PIL (the Python Imaging Library) using the command:

sudo pip install pil

but I get the following message:

Downloading/unpacking PIL
  You are installing a potentially insecure and unverifiable file. Future versions of pip will default to disallowing insecure files.
  Downloading PIL-1.1.7.tar.gz (506kB): 506kB downloaded
  Running setup.py egg_info for package PIL
    WARNING: '' not a valid package name; please use only.-separated package names in setup.py

Installing collected packages: PIL
  Running setup.py install for PIL
    WARNING: '' not a valid package name; please use only.-separated package names in setup.py
    --- using frameworks at /System/Library/Frameworks
    building '_imaging' extension
    clang -fno-strict-aliasing -fno-common -dynamic -g -Os -pipe -fno-common -fno-strict-aliasing -fwrapv -mno-fused-madd -DENABLE_DTRACE -DMACOSX -DNDEBUG -Wall -Wstrict-prototypes -Wshorten-64-to-32 -DNDEBUG -g -Os -Wall -Wstrict-prototypes -DENABLE_DTRACE -arch i386 -arch x86_64 -pipe -IlibImaging -I/System/Library/Frameworks/Python.framework/Versions/2.7/include -I/System/Library/Frameworks/Python.framework/Versions/2.7/include/python2.7 -c _imaging.c -o build/temp.macosx-10.8-intel-2.7/_imaging.o
    unable to execute clang: No such file or directory
    error: command 'clang' failed with exit status 1
    Complete output from command /usr/bin/python -c "import setuptools;__file__='/private/tmp/pip_build_root/PIL/setup.py';exec(compile(open(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-AYrxVD-record/install-record.txt --single-version-externally-managed:
    WARNING: '' not a valid package name; please use only.-separated package names in setup.py

running install

running build

.
.
.
.

copying PIL/XVThumbImagePlugin.py -> build/lib.macosx-10.8-intel-2.7

running build_ext

--- using frameworks at /System/Library/Frameworks

building '_imaging' extension

creating build/temp.macosx-10.8-intel-2.7

creating build/temp.macosx-10.8-intel-2.7/libImaging

clang -fno-strict-aliasing -fno-common -dynamic -g -Os -pipe -fno-common -fno-strict-aliasing -fwrapv -mno-fused-madd -DENABLE_DTRACE -DMACOSX -DNDEBUG -Wall -Wstrict-prototypes -Wshorten-64-to-32 -DNDEBUG -g -Os -Wall -Wstrict-prototypes -DENABLE_DTRACE -arch i386 -arch x86_64 -pipe -IlibImaging -I/System/Library/Frameworks/Python.framework/Versions/2.7/include -I/System/Library/Frameworks/Python.framework/Versions/2.7/include/python2.7 -c _imaging.c -o build/temp.macosx-10.8-intel-2.7/_imaging.o

unable to execute clang: No such file or directory

error: command 'clang' failed with exit status 1

----------------------------------------
Cleaning up…

Could you please help me to install PIL??