for i in range(10): //循環10次，每次加1 賦值給i
print("loop",i)

輸出結果
loop 0
loop 1
loop 2
loop 3
loop 4
loop 5
loop 6
loop 7
loop 8
loop 9

只打印偶數

for i in range(0,10,2): //循環10次，每次加1 賦值給i
print("loop",i)

輸出結果
loop 0

loop 2

loop 4

loop 6

loop 8

隔2個打印一個
for i in range(0,10,3): //循環10次，每次加1 賦值給i
print("loop",i)

輸出結果
loop 0

loop 3

loop 6

loop 9

例1：

age_of_oldboy=56

for i in range(3):
guess_age=int(input("guess_age:"))
if age_of_oldboy==guess_age:
print("yes,you got it")
break
elif age_of_oldboy>guess_age:
print("think smaller")
else:
print("think older")
else:
print("you have tried too many times!")

例2：age_of_oldboy=56
count=0
while count<3 :
guess_age=int(input("guess_age:"))
if age_of_oldboy==guess_age:
print("yes,you got it")
break
elif age_of_oldboy>guess_age:
print("think smaller")
else:
print("think older")
count+=1
if count==3: //進行判斷
continue_confirm=input("do you want to try again?")

第13節 FOR循環