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Re: Python : map and filter vs for loops The underlying implementation of map and filter are different than loops, even though they accomplish the same thing. Which idiom runs fastest can change from version to version. Right now I think list comprehensions are the fastest. So instead of Code: filter(f, range(2,25)), the list comprehension would be Code: [x for x in range(2,25) if f(x)] and instead of Code: map(cube, range(1, 11)) the list comprehension would be Code: [cube(x) for x in range(1,11)]

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)

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*

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

You don't write things like for(int i = 0; i < 10; ++i) in Python very often; instead you do things like for i in range(0, 10).

it would add opcodes to the language (implying a larger, and therefore slower, VM engine)

in the "C" world it is most effectively used (not most commonly) with pointers. There is a direct mapping to some instructions sets that support pre- or post-increment of address registers

usually __iter__() just return self if you have already define the next() method (generator object)

While you are looking at the collections module, consider inheriting from Sequence, Mapping or another abstract base class if that is more appropriate. Here is an example for a Sequence subclass:

if hasattr(self.data[0], "__iter__": return self.data[0].__iter__() return self.data.__iter__()