Replace weird error message?

[Chris Angelico]

On Thu, Mar 17, 2016 at 5:39 AM, Joel Goldstick
<joel.goldstick at gmail.com> wrote:
> can you show the complete code?  It doesn't start with "{:02} I don't think

Actually, yes it does; I can confirm the OP's concern:

$ python3
Python 3.6.0a0 (default:ae76a1046bb9, Mar 17 2016, 05:45:31)
[GCC 5.3.1 20160121] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> "{:02}".format(1)
'01'
>>> "{:02}".format("1")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: '=' alignment not allowed in string format specifier
>>>

And I agree with the OP; the error message should not refer to the
equals sign if that wasn't present. Check the bug tracker at
bugs.python.org to see if it already exists, and if it doesn't, create
an issue. The message _is_ technically correct; here's what the docs
say:

"""
Preceding the width field by a zero ('0') character enables sign-aware
zero-padding for numeric types. This is equivalent to a fill character
of '0' with an alignment type of '='.
"""

However, this is definitely confusing; for positive integers,
alignment '=' is identical to alignment '>', which is (a) the default
for numbers, and (b) valid for strings (using "{:>02}" cures the
error). So go ahead and create the tracker issue, suggesting
alternative wording for the message.

ChrisA