在 Python for 循环中创建计数器
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Creating a counter inside a Python for loop
提问by DIGSUM
Obviously, if we do this, the counter will remain at 0 as it is reset at the start of every iteration:
显然，如果我们这样做，计数器将保持为 0，因为它在每次迭代开始时被重置：
for thing in stuff:
count = 0
print count
count =+1
write_f.write(thing)
But as I have this code inside of function, it does not work to do this either:
但是由于我在函数内部有这段代码，所以这样做也不起作用：
count=0
for thing in stuff:
print count
count =+1
write_f.write(thing)
I have several different indent levels, and no matter how I move count=0about, it either is without effect or throws UnboundLocalError: local variable 'count' referenced before assignment. Is there a way to produce a simple interation counter just inside the for loop itself?
我有几个不同的缩进级别，无论我如何移动count=0，它要么无效，要么抛出UnboundLocalError: local variable 'count' referenced before assignment。有没有办法在 for 循环本身内部生成一个简单的交互计数器？
回答by daniel451
This (creating an extra variable before the for-loop) is notpythonic .
这（在 for 循环之前创建一个额外的变量）不是pythonic 。
The pythonic way to iterate over items while having an extra counter is using enumerate:
在具有额外计数器的同时迭代项目的pythonic方法是使用enumerate：
for index, item in enumerate(iterable):
print(index, item)
So, for example for a list lstthis would be:
因此，例如对于列表，lst这将是：
lst = ["a", "b", "c"]
for index, item in enumerate(lst):
print(index, item)
...and generate the output:
...并生成输出：
0 a
1 b
2 c
You are strongly recommended to always use Python's built-in functionsfor creating "pythonic solutions" whenever possible. There is also the documentation for enumerate.
强烈建议您尽可能使用 Python 的内置函数来创建“pythonic 解决方案”。还有enumerate的文档。
If you need more information on enumerate, you can look up PEP 279 -- The enumerate() built-in function.
如果您需要有关 enumerate 的更多信息，可以查找PEP 279 -- The enumerate() 内置函数。
