1 Circulation

    简化程序中需要重复做的事情，
         比如打印1-100

Print (1)
Print (2)
...
...
above can be solved this way, but 1000,10000, it? It's more troublesome, and it's easier if you use a loop.

2 Loop syntax:

Insert picture description here
The general form of the while statement in Python:
while judgment condition:
statement
also needs to pay attention to the colon and indentation. In addition, there is no do...while loop in Python.

3 The three elements of the cycle

  1  循环体
  2  循环条件
  3  改变循变量的值
	#1 打印 10
	#循环体 是 5行到6行代码
	#循环条件是  number<=10
	#改变循环变量的值 number=number+1  (一般循环体中)
	number = 1
	while number<=10:
		print(number)
		number=number+1

If the above does not change the value of the loop variable, or the while condition is True, it will enter an endless loop

4 Code demo

#Loop while for
#The three elements of loop 1 loop body 2 loop condition 3 change the value of loop variable (in general loop body)

1 print 10

number = 1
while number<=10:
	 print(number)
	 number=number+1

while else

number = 1
while number<=10:
	 print(number)
	 number=number+1
else:
	 print("end")

break interrupt the current loop continue to continue (end the current loop)

number = 1
while number<=10:
	number=number+1
	if number==5:
		continue
	print(number)

Loop nesting

#外层循环执行一次（1），内层循环执行一遍（10）
number1 = 1
while number1<=10:
	number2=1
	while number2<=10:
		print("number1 =",number1," number2 = ",number2)
		if(number2==5):
			break
		number2=number2+1;
	number1=number1+1

Traverse

mes = "hello python"
for a in mes:
	print(a)

names =["admin","tom","jack"]
for  name in names:
	print(name)

range(10) 0-9
for number in range(10):
	print(number)
while True:
	pass #pass 不做任何事情，一般用做占位语句

Teach yourself python--loop control flow