Python：尝试创建一个两变量上下文管理器

Question

I'm new to Python so my guess I'm doing something "syntactically" incorrect. I'm trying to iterate over a grid using row and col as a coordinate system. This my code so far:

from contextlib import contextmanager

# this is the behavior I want
for row in range(10):
    for col in range(10):
        print("row: {}, col: {}".format(row, col))

@contextmanager
def grid_iter():
    for row in range(10):
        for col in range(10):
            yield row, col

# this is my attempt at a context manager so I can reuse this.
with grid_iter() as row, col:
    print("row: {}, col: {}".format(row, col))

This is the output I'm getting:

row: 0, col: 0
row: 0, col: 1
row: 0, col: 2
....
row: 9, col: 7
row: 9, col: 8
row: 9, col: 9
Traceback (most recent call last):
  File "grid_iterator.py", line 17, in <module>
    with grid_iter() as row, col:
AttributeError: __exit__

Answer 1

you should be able to just do:

def grid_iter():
    for row in range(10):
        for col in range(10):
            yield row, col

for row, col in grid_iter():
    print("row: {}, col: {}".format(row, col))

the usage of yield itself makes grid_iter return a generator (you can check this by running print(type(grid_iter())) and then you use it like a normal for-in loop