"list comprehension" in python

[Humble]

List comprehensions apply an arbitrary expression to items in an iterable rather than applying function.

In previous posts I wrote map() , filter()..etc do the same job.. How-ever if you notice, the list comprehension perform “expressions” in a sequence and “map(),”filter()”..etc perform functions on a sequence.. It is important to understand this difference.

For ex: below are examples for list comprehensions.

>>> [2 * x for x in range(1,10)]
[2, 4, 6, 8, 10, 12, 14, 16, 18]
>>> 

>>> [x ** 2 for x in range(10) if x % 2 == 0]
[0, 4, 16, 36, 64]

>>> s= [10,100,20]
>>> [2 * x for x in s]
[20, 200, 40]
>>> 



Though list comprehensions construct lists, they can iterate over any sequence:

When compared to map(), list comprehension has performance advantages.. That said, when you perform list comprehensions , functions are not in picture which basically reduce the stack performance overhead compared to what map() has.. At the same time I would like to point that map() is better than simple "for" loop coding. 

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