Python is Awesome!

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I wrote an earlier post on lambdas and built-in functions in python.

List comprehensions are another really cool feature of python.

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Let's say I have a function isPrime which tells me if a number is prime.
Let's say I want all of the prime numbers ending in "7" less than 1000.
I can do this in one line as follows:

s = [x for x in range(1000) if isPrime(x) and str(x)[-1] == "7"]

This is called a list comprehension and it's very nice as it allows you to turn this:

l = []
for i in range(100):
    if i % 2 == 0:
        l.append(2**i)

into this:

l = [2**i for i in range(100) if i % 2 == 0]

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Dictionary Comprehensions!

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You can also do a similar thing with dictionaries:

d = {str(i):i for i in range(100)}

is essentially this:

d = {"1": 1, "2":2, "3":3, ..., "99":99}

For more information:
http://blog.endpoint.com/2014/04/dictionary-comprehensions-in-python.html