Python generator

Source: rookie tutorial

In Python, functions that use yield are called generators.

Unlike ordinary functions, a generator is a function that returns an iterator and can only be used for iterative operations. It is easier to understand that a generator is an iterator.

In the process of calling the generator to run, the function will pause and save all current running information every time yield is encountered, return the value of yield, and continue to run from the current position when the next() method is executed next time .

Calling a generator function returns an iterator object.

The following example implements the Fibonacci sequence using yield:

import sys

def fibonacci(n): #Generator   function - Fibonacci 
    a, b, counter = 0, 1 , 0
     while True:
         if (counter > n):
             return 
        yield a
        a, b = b, a + b
        counter += 1


f = fibonacci(10)   # f is an iterator, returned by the generator to generate 
while True:
     try :
         print (next(f), end= "  " )
     except StopIteration:
        sys.exit()

Output result: 0 1 1 2 3 5 8 13 21 34 55

For the above example analysis, after the first next(f), the value of the iterator at this time is id(a)

import sys

def fibonacci(n): #Generator   function - Fibonacci 
    a, b, counter = 0, 1 , 0
     while True:
         if (counter > n):
             return 
        yield a
         print (id(a))
         print (id( a))
        a, b = b, a + b
        counter += 1


f = fibonacci(10)   # f is an iterator, returned by the generator to generate 
print (id(next(f)))
 print (next(f))

The output is as follows, found that id(next(f)) == id(a)

1424059840
1424059840
1