Learn Web Development with Python

Name localization

Now that we are familiar with all types of comprehensions and generator expression, let's talk about name localization within them. Python 3.* localizes loop variables in all four forms of comprehensions: list, dict, set, and generator expressions. This behavior is therefore different from that of the for loop. Let's see a simple example to show all the cases:

# scopes.pyA = 100ex1 = [A for A in range(5)]print(A)  # prints: 100ex2 = list(A for A in range(5))print(A)  # prints: 100ex3 = dict((A, 2 * A) for A in range(5))print(A)  # prints: 100ex4 = set(A for A in range(5))print(A)  # prints: 100s = 0for A in range(5):    s += Aprint(A)  # prints: 4

In the preceding code, we declare a global name, A = 100, and then we exercise the ...