漫漫長路

index = 2

for index in range(10):
    print(index)

output:

0
1
2
3
4
5
6
7
8
9
由此程式碼可知for loop 的 index 與全域中的 index 不同，若要使index起始為全域起始，可如此

index = 2

for index in range(index, 10):
    print(index)

output:

2
3
4
5
6
7
8
9

以下嘗試把同名local與global變數放在一起

index = 2

for index in range(10):
    print("local:")
    print(index)
    global index
    print("global:")
    print(index)

ouput結果產生錯誤，兩者皆表示為local變數，並顯示"SyntaxWarning: name 'index' is assigned to before global declaration"錯誤訊息

意思為index該變數在global宣告前已經賦值

再嘗試把 global index放入for loop中

index = 2

for index in range(10):
    global index
    print("global:")
    print(index)

產生與上段程式碼相同錯誤訊息

global index
index = 2

for index in range(10):
    global index
    print("global:")
    print(index)

產生與上段程式碼相同錯誤訊息

for index in range(10):
    print("for index")
    print(index)
    if index >= 0:
        print("if index")
        index = index +1
        print(index)

output:

for index
0
if index
1
for index
1
if index
2
for index
2
if index
3
for index
3
if index
4
for index
4
if index
5
for index
5
if index
6
for index
6
if index
7
for index
7
if index
8
for index
8
if index
9
for index
9
if index
10

Process finished with exit code 0

由上述程式碼可知for 的index與if中的index並不共用, 就像

index_if = 0
for index in range(10):
    print("for index")
    print(index)
    if index >= 0:
        print("if index")
        index_if = index_if +1
        print(index_if)

此程式碼與上段程式碼相同結果

Python has no block scoping, only functions and classes introduce a new scope.

Because you have no function here, there is no need to use a global statement, cows and bullsare already globals.

算了，用while好了

index = 2  # python 默認 index 為全域變數

while index < 10:
    index = index + 1  # 模仿for loop 行為
    print(index)
    index = index + 1  # 動態改變index

參考：https://stackoverflow.com/questions/15725458/how-do-you-create-a-for-loop-with-a-dynamic-range

#此篇文為探討如何把for loop 中的 index 放在 for loop 中其他if等共用，喔，沒有成功，決定用whie代替for loop了