python basis of a review day14

Iterators and generators 
iterator: 
Double Down: Method rarely called directly. In general, triggered by other syntaxes 
may be iterative - protocol may contain an iterative method of __iter__ ( '__iter__' in dir (data)) 
can be for a certain iteration loop 
iterator protocol: containing __iter__ the method and __next__ 
iterators must be iterative, may be iterative approach can be obtained by calling an iterator ITER () 
iterator characteristics: 
    easy to use, and can take all the data fetched once 
    saving memory space 

Builder 
Builder the essence is the iterator 
generator forms 
    generator function 
    generator expression 
generator function: 
    function containing the yield keyword is a generator function of 
    characteristics: 
        after calling the function does not perform the function returns a generator 
        each time the next method invocation when a value to be taken 
        until the end of the last taken, in the next execution will be given 

sketch generator implemented: a file, segment file read from 
the readline 
read (10) 
in front of the read out contents together with a '* ** ', and then return to the caller 
DEF Generator (): 
    for I in Range (20 is): 
        the yield' wow ha% s'% i

g = generator () # call to obtain a generator function generator 
Print (List (G)) 
RET = G .__ Next __ () # g .__ next__ each execution is the value from the generator, the generator indicates functions the code continues execution 
Print (RET) 
NUM = 0 
for I in G: 
    NUM = +. 1 
    IF NUM> 50: 
        BREAK 
    Print (I) 

several methods values from builder 
    Next 
    for 
    cast data types: memory for

Reproduced in: https: //www.cnblogs.com/wang-tan/p/11062954.html