Summary of the use of else in the Python looping statement

Preface

This article discusses Python's for…else and while…else other syntax, which is one of the most common and misunderstood grammatical features in Python.

In Python for , the while Loop has an optional else branch (like the if statement and try statement) that executes after the loop iteration is completed normally. In other words, if we do not exit the loop in any way other than the normal way, then the else branch will be executed. That is, there is no break statement, no return statement, or no exception in the loop body.

Let's take a look at the detailed usage examples below.

I. GENERAL if ELSE usage

x = Trueif X:print ' x is True ' Else:print ' X was not true '

Second, if else quick usage

This if else can be used as a ternary operator.

Mark = 40is_pass = True If Mark >= or Falseprint "pass?" + str (is_pass)

Third, with the FOR keyword one

The else next block of code is executed when the following conditions are met:

1, for the statement execution in the loop completes

2, for the statement in the loop is not interrupted by the break statement

# print ' For loops completed the execution ' for I in range: Print Ielse:print ' For loop completed the execution ' # does not print ' for Loop completed the execution ' for I in range: print i if i = = 5:breakelse:print ' For loop completed the execution '

Iv. with the While keyword

Similar to the above, the else next block of code is executed when the following conditions are met:

1, while the statement execution in the loop completes

2, while the statement in the loop is not interrupted by the break statement

# print ' While loop execution completed ' a = 0loop = 0while a <= 10:print a loop + = 1 A + = 1else:print "While loop execut  Ion completed "# does not print ' while loop execution completed ' a = 50loop = 0while a > 10:print a If loop = = 5:break A + = 1 loop + = 1else:print "While loop execution completed"

V. Use with try except

and try except when used together, if the exception is not thrown, else the statement can be executed.

file_name = "Result.txt" try:f = open (file_name, ' R ') except Ioerror:print ' cannot open ', File_nameelse: # executes only I F file opened properly print file_name, ' has ', Len (F.readlines ()), ' Lines ' f.close ()

Summarize

About the use of else in the circular statement in Python summary to this is basically the end of this article for everyone to learn or use Python or have a certain reference value, hope to everyone can help, if there are questions you can message exchange.