Python 3.0、3.1、3.2中的“ ValueError：格式为零长度的字段名称”错误

I’m trying learn Python (3 to be more specific) and I’m getting this error:

ValueError: zero length field name in format

I googled it and I found out you need to specify the numbers:

a, b = 0, 1
if a < b:
     print('a ({0}) is less than b ({1})'.format(a, b))
else:
     print('a ({0}) is not less than b ({1})'.format(a, b))

And not like the tutorial (from lynda.com) actually says to do:

a, b = 0, 1
if a < b:
     print('a ({}) is less than b ({})'.format(a, b))
else:
     print('a ({}) is not less than b ({})'.format(a, b))

The tutorial im following has Python 3.1, and im using 3.2 and what i read about this error is that this only happens in <3.1 (3.0). Did they undo this in 3.2, or am i doing something wrong?

Also, speak slowly ;) this is literally my first night learning Python and only the 2nd “script” i’ve written in Python.

I’m gonna guess that you are running python 2.6 by accident somehow.

This feature is only available for at least 3.1 if you are using python 3, or 2.7 if you are using python 2.

Python 2.6 and 3.0 require the field numbers. In Python 2.7 and later and 3.1 and later, they can be omitted.

Changed in version 2.7: The positional argument specifiers can be omitted, so ‘{} {}’ is equivalent to ‘{0} {1}’.

python2.6.4>>> print '|{0:^12}|{1:^12}|'.format(3,4)
|     3      |     4     |

If you’re using Eclipse you should look into Window -> Preferences -> PyDev -> Interpreter – Python. There you have a list of interpreters (with name and location). If for your current project you’re using interpreter which is located for example in /usr/bin/python then probably executing /usr/bin/python -V whill give you something like “Python 2.6.6”. And there is your answer like Winston Ewert wrote.

(you can add new interperter by simply clicking “New…” button and giving /usr/bin/python3 as “location”. Then you have probably to change your project settings (Preferences -> PyDev – Interpreter/Grammar).