Python Generator

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Last update: 23-07-2021

p330 ! A generator object knows how to iterate a sequence of values. Unlike list, it does not compute the values at once, it waits to be asked.

 
g = (x**2 for x in range(3))

print(next(g)) # 0
print(next(g)) # 1
print(next(g)) # 4

print(next(g)) # StopIteration Exception

p330 You can also use a for loop to iterate through values. The generator object keeps track of where it is in the sequence.

 
g = (x**2 for x in range(3))

for val in g:
    print(val) # invoke __next__

next(g) # StopIteration Exception

Generators are often used with functions like sum, max, min.

 
sum = sum(x**2 for x in range(5))

print(sum) # 30

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