Python list generation and generator

1 List Builder: List generation is an expression that is used to generate a specific syntactic form of the list.

1. Structure of the underlying statement: [exp for Iter_var in iterable example: A=[f (x) for x in range (Ten)]

2. Working process:

Iterates over each element in the iterable, assigns the result to iter_var each iteration, and then obtains a new calculated value through exp; Finally, all the calculated values obtained by EXP are returned as a new list.

The equivalent of this process:L = [] for iter_var in iterable:

L.append(exp)

Detailed Description: https://www.cnblogs.com/yyds/p/6281453.html

"3" Generator:

1. Function: continuously generate new data according to an algorithm until the end of a specified condition is satisfied.

There are two ways to construct a generator:

• Generated using a similar list-generated form (2*n + 1 for N in range (3, 11))
• Use a function that contains yield to generate

The execution process of the generator:

During execution, the yield keyword is interrupted execution, and the next call continues from where it was last interrupted.

Characteristics of the generator:

• The corresponding data is generated only when it is called
• Record the current location only
• Only next, not prev.

Call of the generator

There are two ways to call the generator to produce a new element:

• Call the built-in next () method
• Using loops to traverse a generator object (recommended)
• Call the Send () method of the Builder object

#Print (List range )#s= (x*2 for x in range )#print (s) #<generator object <genexpr> at 0x000001ebd2e2cfc0> Builder Objects#For I in S:###print (s.__next__ ())#print (Next (s), i) #等价于s. __next__ () Remove an element#print (Next (s))#print (Next (s))#The generator is an iterative object (iterable)#two ways to create a generator#1 (x*2 for x in range (5))#2.yieIddeffoo ():Print('OK')    yield1Print('Ok2')    yield2g=foo ()#Print (g)#For i in Foo ():#print (i)#Next (g)#Next (g)#What is an iterative object (whether there is a _iter_)l=[1,2,3]l.__iter__()defFID (max): N,before,after=0,0,1 whilen<Max:yieldBefore,after=after,before+After N=n+1FID (5)

Python list generation and generator