Python''。format（）：“元组索引超出范围”？

Question

请考虑以下代码段：

>>> def foo(port, out, udp=False, ipv6=False, data=''):
...     if not data:
...             data = 'foo {family} {:port} {direction}'.format(
...                             family=('ipv6' if ipv6 else 'ipv4'),
...                             port=port,
...                             direction=('out' if out else 'in'))
...     return data
...
>>> foo(12345, out=True)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 6, in foo
IndexError: tuple index out of range

据我所知，名字的范围看起来不错。什么是神秘的错误？

Answer 1

观察结肠。将其从端口区域的前面移开：

无论

data = 'foo {family} {port:} {direction}'.format(

或者

data = 'foo {family} :{port} {direction}'.format(

两个选项的结果是：

>>> foo(12345, out=True)
'foo ipv4 12345 out'
>>> foo(12345, out=True)
'foo ipv4 :12345 out'    

Answer 2

{:port}应为{port:}。