Efficient double for loop

问题

What is the most efficient (or Pythonic way) to carry out a double for loop as in below (I know how to do this for list comprehension but not for a single object to be returned):

for i in range(0, 9):
    for j in range(0, 9):
        if self.get(i)[j] == "1":
            return (i, j)

回答1:

>>> next(((i, j)
           for i in range(0, 9)
           for j in range(0, 9)
           if self.get(i)[j] == "1"), None)

This will return None if nothing is found.

See the documentation for next.

The first parameter is a generator. You need this if you supply None as the second parameter. Otherwise you can skip the extra parentheses. If you don't supply None though it will throw a StopIteration exception if nothing is found.

来源：https://stackoverflow.com/questions/32976373/efficient-double-for-loop