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To do element-wise operations on a list - for example, to produce a list consisting of each element of list A multiplied by 2 Method 1 [2*x for x in A] - this technique is called list comprehension Method 2 if you have defined a function double(x) which doubles x map(double, A) Method 3 define the function that doubles x on the fly, anonymously map(lambda x: 2*x, A)

If print() is a function, it would be much easier to replace it within one module (just def print(*args):...) or even throughout a program (e.g. by putting a different function in __builtin__.print). As it is, one can do this by writing a class with a write() method and assigning that to sys.stdout -- that's not bad, but definitely a much larger conceptual leap, and it works at a different level than print.

*name must occur before **name.

keys = sorted(keywords.keys()) for kw in keys: print kw, ":", keywords[kw]

Note that the list of keyword argument names is created by sorting the result of the keywords dictionary’s keys() method before printing its contents; if this is not done, the order in which the arguments are printed is undefined

The subprocess module allows you to spawn new processes, connect to their input/output/error pipes, and obtain their return codes. This module intends to replace several other, older modules and functions, such as: os.system os.spawn* os.popen* popen2.* commands.*

The Boost Python Library is a framework for interfacing Python and C++. It allows you to quickly and seamlessly expose C++ classes functions and objects to Python, and vice-versa, using no special tools -- just your C++ compiler. It is designed to wrap C++ interfaces non-intrusively, so that you should not have to change the C++ code at all in order to wrap it, making Boost.Python ideal for exposing 3rd-party libraries to Python. The library's use of advanced metaprogramming techniques simplifies its syntax for users, so that wrapping code takes on the look of a kind of declarative interface definition language (IDL).

keyword arguments with default values can go a long way.

In Python, I think it's more accepted to use duck typing -- asking what an object can do, rather than what it is

it goes against the spirit of Python to worry a lot about what types are passed into methods

class foo: def __init__(self, n): self.n = n def __call__(self, i): self.n += i return self.n

function foo (n) { return function (i) { return n += i } }

From PyQt4.6, PyQt has two APIs, API#1 (the original), and API#2 (new). API#2 is more Pythonic and eliminates QString and QVariant, and is a bit nicer to use. API#1 remains best for those using PyQt to prototype C++/Qt applications. API#1 is the default for PyQt4.x with Python 2.x, and for PyQt4.0-4.5 with Python 3.x. API#2 is the default for PyQt4.6+ with Python 3.x, and for PySide.

most of the changes affect uses of QDataStream, QSettings, and QTextStream, and of course any use of QString methods (since in API#2, QString is gone, so we use str).

To convert any particular example to PySide the steps are as follows: Replace python3 in the first line with python. Add the following statements before the first import: from __future__ import division from __future__ import print_function from future_builtins import * Replace PyQt4 with PySide throughout (e.g., in the imports) If using Python 2.6 replace {} in format strings with {0}, {1}, etc., as appropriate. Add [0] at the end of every QFileDialog.*() function call. (In PyQt these return a—possibly empty—filename; in PySide they return a filename–filter 2-tuple, but all the examples only need the filename.) Replace QT_VERSION_STR with qVersion(). Replace PYQT_VERSION_STR with PySide.__version__; you will also need to add import PySide in the imports after the future imports. Replace @pyqtSignature with @Slot. Replace def isAlive(qobj): ... with def isAlive(qobj): return True. (There is currently no PySide equivalent.) Replace chr with unichr.

The central component of any game, from a programming standpoint, is the game loop. The game loop allows the game to run smoothly regardless of a user's input or lack thereof. Most traditional software programs respond to user input and do nothing without it. For example, a word processor formats words and text as a user types. If the user doesn't type anything, the word processor does nothing. Some functions may take a long time to complete, but all are initiated by a user telling the program to do something. Games, on the other hand, must continue to operate regardless of a user's input. The game loop allows this. A highly simplified game loop, in pseudocode, might look something like this: while( user doesn't exit ) check for user input run AI move enemies resolve collisions draw graphics play sounds end while

common ways to use doctest: To check that a module’s docstrings are up-to-date by verifying that all interactive examples still work as documented. To perform regression testing by verifying that interactive examples from a test file or a test object work as expected. To write tutorial documentation for a package, liberally illustrated with input-output examples. Depending on whether the examples or the expository text are emphasized, this has the flavor of “literate testing” or “executable documentation”.

Running the module as a script causes the examples in the docstrings to get executed and verified

The file content is treated as if it were a single giant docstring; the file doesn’t need to contain a Python program! For example, perhaps example.txt contains this

It's not an operator as such, so it doesn't really have a name, but it is defined as a "syntactic rule". So it should be called: "the keyword argument unpacking syntax"

# usually a tuple, always an iterable*

# usually a dict, always a mapping*

Comprehensions are just a simple form of iterators. Generators are just a simple form of iterators

The first argument of every class method, including the __init__() method, is always a reference to the current instance of the class. By convention, this argument is named self.

self is not a reserved word in Python, merely a naming convention