The while loop of the Python looping statement 22

One, cycle mechanism and application scenario

1.while Cycle

Used to write generic iterative structures (non-traversal);

The top test executes the loop body as true, and repeats the test several times until the other statement after the loop is executed.

2.for Cycle

A general-purpose sequence iterator used to traverse the elements within any ordered sequence object;

Can be used for strings, tuples, lists, and other built-in iterative objects, as well as new objects created through the class;

3.python also provides some tools to perform covert iterations

In member relationship testing

List parsing

Map, reduce, and filter functions

Two, while loop

1. Syntax format

While Boolean_exception:while_suiteelse Else_suite

2. Grammatical features

1) The Else branch is an optional part;

2) As long as the boolean_exception result is true, the loop executes;

3) The boolean_exception result is false when the loop terminates, if there is an else branch, it will be executed once;

4) Break: Encounter break out of the inner layer of the loop;

5) Continue: Encounter continue jump to the beginning of the nearest layer loop;

6) Pass: Placeholder statement;

7) Else code block: The loop terminates normally and else does not execute if the loop termination is caused by a break.

While slicing in [29]: url =  ' www.magedu.com ' in [30]: while url:    ....:     print url   ....:      url = url[1:]   ....:      www.magedu.comww.magedu.comw.magedu.com.magedu.commagedu.comagedu.comgedu.comedu.comdu.comu.com.comcomomm// While generating the digital in [33]: x = 0;y = 10in [35]: while x < y:    ....:     print x,   ....:      x += 1   ....:     0 1 2 3 4  5 6 7 8 9//while Branch Statement in [37]: url =  ' www.magedu.com ' In [38]:  while url:   ....:     print url    : &NBSP;&NBSP;&NBSP;&NBSP;&NBSP;URL&NBSP;=&NBSP;URL[:-1]&Nbsp;  ....: else:   ....:     print  "Game  over! "    ....:      Www.magedu.comwww.magedu.cowww.magedu.cwww.magedu.www.mageduwww.magedwww.magewww.magwww.mawww.mwww.wwwwwwGame  over!//while Branch statement encountered break, jumping out of the inner loop in [39]: url =  ' www.magedu.com '; x = 0in  [40]: while url:   ....:     print url    ....:     url = url[:-1]   ....:      x += 1   ....:     if x >  7:   ....:         break    ....: else:   ....:     print  "Game over"     ....:     www.magedu.comwww.magedu.cowww.magedu.cwww.maGedu.www.mageduwww.magedwww.magewww.mag 

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The while loop of the Python looping statement 22