diff options
| -rw-r--r-- | Doc/library/typing.rst | 23 | ||||
| -rw-r--r-- | Lib/typing.py | 4 |
2 files changed, 13 insertions, 14 deletions
diff --git a/Doc/library/typing.rst b/Doc/library/typing.rst index ba2845e..63bd62d 100644 --- a/Doc/library/typing.rst +++ b/Doc/library/typing.rst @@ -2604,10 +2604,10 @@ Functions and decorators .. function:: reveal_type(obj, /) - Reveal the inferred static type of an expression. + Ask a static type checker to reveal the inferred type of an expression. When a static type checker encounters a call to this function, - it emits a diagnostic with the type of the argument. For example:: + it emits a diagnostic with the inferred type of the argument. For example:: x: int = 1 reveal_type(x) # Revealed type is "builtins.int" @@ -2615,22 +2615,21 @@ Functions and decorators This can be useful when you want to debug how your type checker handles a particular piece of code. - The function returns its argument unchanged, which allows using - it within an expression:: + At runtime, this function prints the runtime type of its argument to + :data:`sys.stderr` and returns the argument unchanged (allowing the call to + be used within an expression):: - x = reveal_type(1) # Revealed type is "builtins.int" + x = reveal_type(1) # prints "Runtime type is int" + print(x) # prints "1" + + Note that the runtime type may be different from (more or less specific + than) the type statically inferred by a type checker. Most type checkers support ``reveal_type()`` anywhere, even if the name is not imported from ``typing``. Importing the name from - ``typing`` allows your code to run without runtime errors and + ``typing``, however, allows your code to run without runtime errors and communicates intent more clearly. - At runtime, this function prints the runtime type of its argument to stderr - and returns it unchanged:: - - x = reveal_type(1) # prints "Runtime type is int" - print(x) # prints "1" - .. versionadded:: 3.11 .. decorator:: dataclass_transform(*, eq_default=True, order_default=False, \ diff --git a/Lib/typing.py b/Lib/typing.py index 61b88a5..d7d7935 100644 --- a/Lib/typing.py +++ b/Lib/typing.py @@ -3301,7 +3301,7 @@ class TextIO(IO[str]): def reveal_type[T](obj: T, /) -> T: - """Reveal the inferred type of a variable. + """Ask a static type checker to reveal the inferred type of an expression. When a static type checker encounters a call to ``reveal_type()``, it will emit the inferred type of the argument:: @@ -3313,7 +3313,7 @@ def reveal_type[T](obj: T, /) -> T: will produce output similar to 'Revealed type is "builtins.int"'. At runtime, the function prints the runtime type of the - argument and returns it unchanged. + argument and returns the argument unchanged. """ print(f"Runtime type is {type(obj).__name__!r}", file=sys.stderr) return obj |