A basic example of the while loop:
Example 1: determining whether greater than 50
Example 2: Print on demand multiplication formulas
Example 3: infinite loop
while True：
print （“true”）
Two, for circulation
1, the common range for usage cycle:
for i in (0,3,4,5,7,40): # include all
for i in range (0,10): #range method 0-9, the last is not included
for i in range (10): # default starting from 0
2, Example 1: Find the odd
Three, while, for the three key words cycle may
break、continue、exit
break: ends the cycle
continue: the end of this cycle, the next cycle continues
exit: Exit the program