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Python Is an easy to learn 、 Powerful programming language . It provides an efficient high-level data structure , It's also a simple and effective way of object-oriented programming .Python Elegant grammar and dynamic typing and the essence of interpretive language , Make it an ideal language for scripting and rapid application development on most platforms . Now let's introduce while Circulation and for How to use circular statements .
When solving practical problems , We often encounter different operation conditions , Or often encounter the need to repeat the same or similar operations .Python Judgment and loop statements are provided to solve these problems .
Python Medium for Loops are often used to traverse lists 、 Tuples 、 Elements in sequences such as strings and dictionaries . for The basic format of the syntax structure of circular statements ：
for Variable in Sequence :
Sentence block
example 1,for Loop through a string .
for x in "python":
print(x)
Program running effect .
for Circular statements are often associated with range() Functions together ,range() The function is Python Built in functions for , You can create a list of integers .range() The syntax of the function is ： （1） Count from start Start , The default is 0 Start . （2） Count to stop end , But does not include stop. （3） step , The default is 1.
range([start,]stop[,step])
example 2：
range(5) Equivalent to range(0,5) range(0,5) yes [0,1,2,3,4] range(0,5) Equivalent to range(0,5,1)
example 3： use for Statement seeking S=1+2+3+…+100 Value .
S = 0 # Create variables S, The assignment is 0
for i in range(1, 101): # Loop variable i from 1 Loop to 100
S += i # Sum up , Put the results in S in
print("S=1+2+3+…+100=", S) # Output S Value
Program running effect .
while The basic format of a loop statement is as follows ：
while Judge the condition :
Sentence block # The loop body
Tips :while The loop statement is “ First judge , After execution ”. If the conditions are not met when the cycle is just entered , Then the loop body does not execute . The other thing to note is that , There must be a sentence to modify the judgment conditions , Make it false , Otherwise, there will be “ Dead cycle ”.
example 1： Programming , seek S=1+2+3+…+100 Value .
i = 1 # Create variables i, The assignment is 1
S = 0 # Create variables S, The assignment is 0
while i <= 100: # loop , When i>100 End of time
S += i # Sum up , Put the results in S in
i += 1 # Variable i Add 1
print("S=1+2+3+…+100=", S) # Output S Value
Program running effect , Be careful . （1） Variable initialization description should be complete 、 accuracy . （2） There should be a statement in the loop body that makes the loop tend to end .
The loop body of a loop statement contains another complete loop structure , It's called loop nesting . (1) The circulation embedded in the circulation is called internal circulation . (2) A cycle embedded with an inner cycle is called an outer cycle . (3) Loops can also be nested in embedded loops , This is called multiple cycles . Two kinds of loop statements while Statement and for Statements can be nested with each other , Free combination . The outer circulation body may contain one or more inner circulation structures . Be careful : Each cycle must contain , No cross is allowed between them .
example 1： Write a program , Output the following multiplication table .
for x in range(1, 10): # Loop variable x from 1 Loop to 9
for y in range(1, x + 1): # Loop variable y from 1 Loop to x+1
print(y, "*", x, "=", x * y, "", end="") # Output multiplication expression
print("") # Output empty string , The function is to wrap
Program running effect .
1、Python Programming case tutorial
The above is about Python Of while Circulation and for How to use circular statements . How to use , You can refer to it , Relevant knowledge will be continuously updated later , Make progress together .
