for循环中的Python循环计数器 [英] Python loop counter in a for loop

问题描述

在我下面的示例代码中，是否真的需要 counter = 0，或者是否有更好、更 Python 的方法来访问循环计数器?我看到了一些与循环计数器相关的 PEP，但它们要么被推迟，要么被拒绝(PEP 212 和 PEP 281).

In my example code below, is the counter = 0 really required, or is there a better, more Python, way to get access to a loop counter? I saw a few PEPs related to loop counters, but they were either deferred or rejected (PEP 212 and PEP 281).

这是我的问题的一个简化示例.在我的实际应用程序中，这是通过图形完成的，并且必须在每一帧重新绘制整个菜单.但这以一种易于复制的简单文本方式展示了它.

This is a simplified example of my problem. In my real application this is done with graphics and the whole menu has to be repainted each frame. But this demonstrates it in a simple text way that is easy to reproduce.

也许我还应该补充一点，我使用的是 Python 2.5，尽管我仍然对是否有特定于 2.6 或更高版本的方法感兴趣.

Maybe I should also add that I'm using Python 2.5, although I'm still interested if there is a way specific to 2.6 or higher.

# Draw all the options, but highlight the selected index
def draw_menu(options, selected_index):
    counter = 0
    for option in options:
        if counter == selected_index:
            print " [*] %s" % option
        else:
            print " [ ] %s" % option
        counter += 1


options = ['Option 0', 'Option 1', 'Option 2', 'Option 3']

draw_menu(option, 2) # Draw menu with "Option2" selected

运行时输出:

 [ ] Option 0
 [ ] Option 1
 [*] Option 2
 [ ] Option 3

推荐答案

使用 enumerate() 像这样:

def draw_menu(options, selected_index):
    for counter, option in enumerate(options):
        if counter == selected_index:
            print " [*] %s" % option
        else:
            print " [ ] %s" % option    

options = ['Option 0', 'Option 1', 'Option 2', 'Option 3']
draw_menu(options, 2)

注意:如果需要，您可以选择将括号放在 counter, option 周围，例如 (counter, option)，但它们是无关紧要的，通常不包括在内.

Note: You can optionally put parenthesis around counter, option, like (counter, option), if you want, but they're extraneous and not normally included.

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