str.format() raises KeyError

问题

The following code raises a KeyError exception:

addr_list_formatted = []
addr_list_idx = 0

for addr in addr_list: # addr_list is a list
    addr_list_idx = addr_list_idx + 1
    addr_list_formatted.append("""
        "{0}"
        {
        "gamedir"  "str"
        "address"  "{1}"
        }
    """.format(addr_list_idx, addr))

Why?

I am using Python 3.1.

回答1:

The problem is those { and } characters you have there that don't specify a key for formatting. You need to double them up, so change your code to:

addr_list_formatted.append("""
    "{0}"
    {{
    "gamedir"  "str"
    "address"  "{1}"
    }}
""".format(addr_list_idx, addr))

来源：https://stackoverflow.com/questions/2755201/str-format-raises-keyerror