Python Learning Notes (Ⅱ)--loops/selections/functions

I. Cyclic structure

In Python, there are two operations for the For loop and while loop, with no do......while statements.

1.for Loop:

Unlike the common notation for loops in other languages such as for (int i=0;i<10;i++), the for loop in Python is more similar to the foreach structure:

# #举例: Traverse all letters that output a single word
For letter in'Python':
　　Print(' current letter:'+   letters ')  

Contrast:

string " Python " ; foreach (charin  str) {    Console.WriteLine (" current Letter:"+C) ;       }

We sometimes involve operations or judgments on an array, a list, or a dictionary index or subscript, and in Python we provide a for-I in range (start index, end index) operation:

 #   #举例: Outputs the first 3 letters of a list  list = [ " c#  " , Span style= "COLOR: #800000" > " java  " ,  " python   ", "  c   ", "  c++   " "  for  I in  Range (0,2) #      #注意索引下表是从0开始, this notation is equivalent to the for (int i=0;i<=2;i++)  print  (List[i]) 

In Python3, we can even make range start with a specified number and specify different increments (even negative numbers, sometimes referred to as ' stride '):

For example: For i in range (0, 3) : print(i ), this notation is equivalent to the for (int i=0;i<=10;i=i+3)

< Span class= "Hl-number" >2.while loop:

The basic syntax is as follows:

 while Judging Condition:    Loop statement

When judging the condition as a perpetual condition, while is an infinite loop, it is more common to handle real-time requests or other looping operations:

 while 1==1:    ##循环语句

Use Crtl+c to jump directly out of the loop

3. Use break with continue for loop control:

 var = while  var > 0:  print  ( '   "  , var) var  = Var-1 if  var = = 5:  break
      #   #break直接跳出整个循环  print  ("  good bye!   ") 

var = ten while                   var > 0:                 = var-1   if var = = 5:             #  continue to skip this Loop's remaining code, jump directly into the next loop      continue   print (' current variable value:')  , var)print ("good bye! ")

Python Learning Notes (Ⅱ)--loops/selections/functions