JitterMan <[email protected]> added the comment:
I believe it is worth fixing as it clears up some rather glaring
inconsistencies␣
and enables a useful capability. Specifically,
1. Formatted string literals and the string format method are currently
inconsistent in the way that they handle double braces in the format
specifier.
>>> x = 42
>>> import datetime
>>> now = datetime.datetime.now()
>>> f'{now:x{{x}}x}'
'x{42}x'
>>> '{:x{{x}}x}'.format(now)
'x{x}x'
2. Formatted string literals currently seem inconsistent in the way they handle
handle doubled braces.
In the base string doubling the braces escapes them.
>>> f'x{{x}}x'
'x{x}x'
In the replacement expression doubling the braces escapes them.
>>> f'{f"x{{x}}x"}'
'x{x}x'
In the format specifier doubling the braces does not escape them.
>>> f'{now:x{{x}}x}'
'x{42}x'
3. Currently there is no way I know of escape the braces in the format
specifier.
4. Allowing the braces to be escaped in the format specifier allows the user to
defer the interpretation of the of a format specifier so that it is
evaluated
by a format function inside the object rather than being evaluated in the
current context. That seems like a generally useful feature.
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Python tracker <[email protected]>
<https://bugs.python.org/issue39601>
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