今天介紹另一個循環判斷式 for循環，首先，先寫一個很簡單的 for循環的代碼
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
for i in range(10):
print("loop:", i)
---------------執行結果---------------
loop: 0
loop: 1
loop: 2
loop: 3
loop: 4
loop: 5
loop: 6
loop: 7
loop: 8
loop: 9
Process finished with exit code 0
那 for循環是怎麼跑的呢？請看下圖
接下來我們再來延伸一下，如果我想要把一開始的 form循環 每隔一個數字才打印出來，要怎麼實現？
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
for i in range(0, 10, 2):
print("loop:", i)
---------------執行結果---------------
loop: 0
loop: 2
loop: 4
loop: 6
loop: 8
Process finished with exit code 0
這樣就可以達成目的了，接下來要再提升一點難度，如何把 for循環 判斷式套用到猜年紀的遊戲中呢？忘記了請參考Python 基礎 - while流程判斷 的最後一個代碼
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
age_of_ironman = 35
for i in range(3):
guess_age = int(input("guess age:"))
if guess_age == age_of_ironman:
print("Bingo, You got it!!!")
break
elif guess_age > age_of_ironman:
print("You may think smaller...")
else:
print("You may think bigger...")
else:
print("You have tried too many, exit")
---------------執行結果---------------
# 故意猜超過三次，看看結果
guess age:1
You may think bigger...
guess age:2
You may think bigger...
guess age:3
You may think bigger...
You have tried too many, exit
Process finished with exit code 0
# 先試試在三次內打對密碼，看看結果
guess age:4
You may think bigger...
guess age:35
Bingo, You got it!!!
Process finished with exit code 0
上面的代碼因為用了 for循環 就不需要計數器了，因此就把 count = 0 跟 count += 1 給刪除了，就可以完成了，但是這段代碼的 for循環 又是怎麼跑的呢？請看下圖
再來再提升一下難度，這次需求是要讓這個遊戲可以讓任隨便玩，不過一樣要每三次問一下，要不要繼續玩？
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
age_of_ironman = 35
count = 0
while count < 3:
guess_age = int(input("guess age:"))
if guess_age == age_of_ironman:
print("Bingo, You got it!!!")
break
elif guess_age > age_of_ironman:
print("You may think smaller...")
else:
print("You may think bigger...")
count += 1
if count == 3:
countine_confirm = input("Do you want to keep go in ? (y/n)")
if countine_confirm != 'n':
count = 0
else:
print("You have tried too many, exit")
---------------執行結果---------------
# 故意猜錯三次，第二次詢問時，選n
guess age:1
You may think bigger...
guess age:2
You may think bigger...
guess age:3
You may think bigger...
Do you want to keep go in ? (y/n)
guess age:4
You may think bigger...
guess age:5
You may think bigger...
guess age:6
You may think bigger...
Do you want to keep go in ? (y/n)n
You have tried too many, exit
Process finished with exit code 0
有發現上面代碼有一個怪怪的地方嗎？請看下圖說明
所以我們只要把需要註解或是刪除那二碼代碼即可
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
age_of_ironman = 35
count = 0
while count < 3:
guess_age = int(input("guess age:"))
if guess_age == age_of_ironman:
print("Bingo, You got it!!!")
break
elif guess_age > age_of_ironman:
print("You may think smaller...")
else:
print("You may think bigger...")
count += 1
if count == 3:
countine_confirm = input("Do you want to keep go in ? (y/n)")
if countine_confirm != 'n':
count = 0
---------------執行結果---------------
# 故意猜錯三次，第二次詢問時，選n
guess age:1
You may think bigger...
guess age:2
You may think bigger...
guess age:3
You may think bigger...
Do you want to keep go in ? (y/n)y
guess age:4
You may think bigger...
guess age:5
You may think bigger...
guess age:6
You may think bigger...
Do you want to keep go in ? (y/n)n
Process finished with exit code 0
知識點：
- 語法：
range(start, stop[, step])裡面的step 預設是 1
參考資料：