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Update docs to reflect new behavior around backslashes in expressions (not allowed), matching recent changes to PEP 498.

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Jason R. Coombs 2016-11-06 11:27:17 -05:00
parent 1c92a76a69
commit f66f03bd35
1 changed files with 12 additions and 7 deletions
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19
Doc/reference/lexical_analysis.rst
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@ -679,17 +679,22 @@ Some examples of formatted string literals::
A consequence of sharing the same syntax as regular string literals is
that characters in the replacement fields must not conflict with the
quoting used in the outer formatted string literal. Also, escape
sequences normally apply to the outer formatted string literal,
rather than inner string literals::
quoting used in the outer formatted string literal::
f"abc {a["x"]} def" # error: outer string literal ended prematurely
f"abc {a[\"x\"]} def" # workaround: escape the inner quotes
f"abc {a['x']} def" # workaround: use different quoting
f"newline: {ord('\n')}" # error: literal line break in inner string
f"newline: {ord('\\n')}" # workaround: double escaping
fr"newline: {ord('\n')}" # workaround: raw outer string
Backslashes are not allowed in format expressions and will raise
an error::
f"newline: {ord('\n')}" # raises SyntaxError
To include a value in which a backslash escape is required, create
a temporary variable.
>>> newline = ord('\n')
>>> f"newline: {newline}"
'newline: 10'
See also :pep:`498` for the proposal that added formatted string literals,
and :meth:`str.format`, which uses a related format string mechanism.