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author | Serhiy Storchaka <storchaka@gmail.com> | 2020-02-14 01:53:59 +0200 |
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committer | GitHub <noreply@github.com> | 2020-02-13 18:53:59 -0500 |
commit | cebe9ee988837b292f2c571e194ed11e7cd4abbb (patch) | |
tree | a26d7b4981f803cf451c32a240f69b22019ef235 | |
parent | a2963f09629a0a8c63e9acef79c1dcc0a040ddb6 (diff) | |
download | cpython-git-cebe9ee988837b292f2c571e194ed11e7cd4abbb.tar.gz |
bpo-39545: Document restrictions on "await" and "async for" in f-strings. (GH-18459)
-rw-r--r-- | Doc/reference/compound_stmts.rst | 2 | ||||
-rw-r--r-- | Doc/reference/lexical_analysis.rst | 9 |
2 files changed, 10 insertions, 1 deletions
diff --git a/Doc/reference/compound_stmts.rst b/Doc/reference/compound_stmts.rst index b4e95b90db..8d050a69a9 100644 --- a/Doc/reference/compound_stmts.rst +++ b/Doc/reference/compound_stmts.rst @@ -730,7 +730,7 @@ Functions defined with ``async def`` syntax are always coroutine functions, even if they do not contain ``await`` or ``async`` keywords. It is a :exc:`SyntaxError` to use ``yield from`` expressions in -``async def`` coroutines. Using ``await`` in :keyword:`f-strings` will also produce a :exc:`SyntaxError`. +``async def`` coroutines. An example of a coroutine function:: diff --git a/Doc/reference/lexical_analysis.rst b/Doc/reference/lexical_analysis.rst index bee02443e6..3a03b94716 100644 --- a/Doc/reference/lexical_analysis.rst +++ b/Doc/reference/lexical_analysis.rst @@ -683,6 +683,15 @@ can contain line breaks (e.g. in triple-quoted strings), but they cannot contain comments. Each expression is evaluated in the context where the formatted string literal appears, in order from left to right. +.. index:: + keyword: await + single: async for; in comprehensions + +An :keyword:`await` expression and comprehensions containing an +:keyword:`async for` clause are illegal in the expression in formatted +string literals. (The reason is a problem with the implementation --- +this restriction is lifted in Python 3.7). + If a conversion is specified, the result of evaluating the expression is converted before formatting. Conversion ``'!s'`` calls :func:`str` on the result, ``'!r'`` calls :func:`repr`, and ``'!a'`` calls :func:`ascii`. |