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Stephen ColeCourses Plus Student 15,690 Points
What is the for loop inside the sum function called?
In the final example, Kenneth creates a function that calculates the sum function that seems to do a list comprehension. What is it and why does it work?
Chris FreemanTreehouse Moderator 68,332 Points
It like a list comprehension, but in this case it is a generator expression. It behaves much like a list comprehension, but gives the advantage of a generator in terms of minimal memory usage.
# standard list comprehension >>> [x**2 for x in range(5)] [0, 1, 4, 9, 16] # generator expression - using parens instead of square brackets >>> (x**2 for x in range(5)) <generator object <genexpr> at 0x000000000119D8E0> # expand generator using list >>> list(x**2 for x in range(5)) [0, 1, 4, 9, 16] # using list comprehension as an argument to sum() >>> sum([x**2 for x in range(5)]) 30 # using generator expression (without square brackets) >>> sum(x**2 for x in range(5)) 30 # Not in a comprehension or generator context is a syntax error >>> x**2 for x in range(5) File "<stdin>", line 1 x**2 for x in range(5) ^ SyntaxError: invalid syntax