Python: can't print dictionary key and value

Question

This is a very simple block of code and I don't understand what I'm doing wrong:

import sys

o_dict = {'a': 10, 'b': 0, 'c': 20}
for key, val in o_dict.iteritems():
    if val < 1:
        sys.exit("Key: {}, Val: {}.").format(key, val)

I'd expect the output to be:

Key: b, Val: 0.

but instead it's always:

Key: {}, Val: {}.

What's happenning?

Answer 1

You have your format method on the exit method, not on the string. This is what you have:

sys.exit("Key: {}, Val: {}.").format(key, val)
#                           ^ wrong

this is what you want:

sys.exit("Key: {}, Val: {}.".format(key, val))
#                                            ^ right

Answer 2

错字：

sys.exit("Key: {}, Val: {}.".format(key, val))