inspect.signature with PEP 563
The following code:
import inspect
from typing import NamedTuple
class Example(NamedTuple):
a: str
if __name__== "__main__":
signature: inspect.Signature = inspect.signature(Example)
print(signature)
outputs:
(a: str)
However when enabling PEP 563 – Postponed Evaluation of Annotations:
from __future__ import annotations
import inspect
from typing import NamedTuple
class Example(NamedTuple):
a: str
if __name__== "__main__":
signature: inspect.Signature = inspect.signature(Example)
print(signature)
The output is:
(a: 'str')
How can I get the exact same object of type inspect.Signature with PEP 563 like without it?
python python-3.x types python-3.7 static-typing
edited Nov 20 '18 at 10:46
usr2564301
17.8k73370
asked Nov 20 '18 at 10:29
Tobias HermannTobias Hermann
2,96022151
add a comment |
The following code:
import inspect
from typing import NamedTuple
class Example(NamedTuple):
a: str
if __name__== "__main__":
signature: inspect.Signature = inspect.signature(Example)
print(signature)
outputs:
(a: str)
However when enabling PEP 563 – Postponed Evaluation of Annotations:
from __future__ import annotations
import inspect
from typing import NamedTuple
class Example(NamedTuple):
a: str
if __name__== "__main__":
signature: inspect.Signature = inspect.signature(Example)
print(signature)
The output is:
(a: 'str')
How can I get the exact same object of type inspect.Signature with PEP 563 like without it?
python python-3.x types python-3.7 static-typing
edited Nov 20 '18 at 10:46
usr2564301
17.8k73370
asked Nov 20 '18 at 10:29
Tobias HermannTobias Hermann
2,96022151
The whole point of that PEP is to not get the same object... You'll have to evaluate the string usingexecor the like.
– Bakuriu
Nov 22 '18 at 22:59
add a comment |
The following code:
import inspect
from typing import NamedTuple
class Example(NamedTuple):
a: str
if __name__== "__main__":
signature: inspect.Signature = inspect.signature(Example)
print(signature)
outputs:
(a: str)
However when enabling PEP 563 – Postponed Evaluation of Annotations:
from __future__ import annotations
import inspect
from typing import NamedTuple
class Example(NamedTuple):
a: str
if __name__== "__main__":
signature: inspect.Signature = inspect.signature(Example)
print(signature)
The output is:
(a: 'str')
How can I get the exact same object of type inspect.Signature with PEP 563 like without it?
python python-3.x types python-3.7 static-typing
edited Nov 20 '18 at 10:46
usr2564301
17.8k73370
asked Nov 20 '18 at 10:29
Tobias HermannTobias Hermann
2,96022151
The following code:
import inspect
from typing import NamedTuple
class Example(NamedTuple):
a: str
if __name__== "__main__":
signature: inspect.Signature = inspect.signature(Example)
print(signature)
outputs:
(a: str)
However when enabling PEP 563 – Postponed Evaluation of Annotations:
from __future__ import annotations
import inspect
from typing import NamedTuple
class Example(NamedTuple):
a: str
if __name__== "__main__":
signature: inspect.Signature = inspect.signature(Example)
print(signature)
The output is:
(a: 'str')
How can I get the exact same object of type inspect.Signature with PEP 563 like without it?
python python-3.x types python-3.7 static-typing
python python-3.x types python-3.7 static-typing
edited Nov 20 '18 at 10:46
usr2564301
17.8k73370
asked Nov 20 '18 at 10:29
Tobias HermannTobias Hermann
2,96022151
edited Nov 20 '18 at 10:46
usr2564301
17.8k73370
asked Nov 20 '18 at 10:29
Tobias HermannTobias Hermann
2,96022151
edited Nov 20 '18 at 10:46
usr2564301
17.8k73370
edited Nov 20 '18 at 10:46
usr2564301
17.8k73370
edited Nov 20 '18 at 10:46
usr2564301
17.8k73370
17.8k73370
asked Nov 20 '18 at 10:29
Tobias HermannTobias Hermann
2,96022151
asked Nov 20 '18 at 10:29
Tobias HermannTobias Hermann
2,96022151
asked Nov 20 '18 at 10:29
Tobias HermannTobias Hermann
2,96022151
2,96022151
The whole point of that PEP is to not get the same object... You'll have to evaluate the string usingexecor the like.
– Bakuriu
Nov 22 '18 at 22:59
add a comment |
The whole point of that PEP is to not get the same object... You'll have to evaluate the string usingexecor the like.
– Bakuriu
Nov 22 '18 at 22:59
The whole point of that PEP is to not get the same object... You'll have to evaluate the string using
exec or the like.– Bakuriu
Nov 22 '18 at 22:59
The whole point of that PEP is to not get the same object... You'll have to evaluate the string using
exec or the like.– Bakuriu
Nov 22 '18 at 22:59
add a comment |
2 Answers
2
active
oldest
votes
The point of using PEP 536 is to not evaluate the annotations unless needed. The signature merely reports on the annotations.
If for your purposes you need to have the annotations resolved, you have to do so yourself. PEP 536 tells documents how you do this:
For code that uses type hints, the
typing.get_type_hints(obj, globalns=None, localns=None)function correctly evaluates expressions back from its string form.
[...]
For code which uses annotations for other purposes, a regular eval(ann, globals, locals) call is enough to resolve the annotation.
You could even use the typing.get_type_hints() function to assign back to __annotations__ before getting the signature:
import typing
Example.__new__.__annotations__ = typing.get_type_hints(Example.__new__)
signature: inspect.Signature = inspect.signature(Example)
Doing this is safe even if from __future__ import annotations had not been used.
answered Nov 22 '18 at 23:38
Martijn Pieters♦Martijn Pieters
714k13724952307
Perfect. Thanks. I'll award the bounty tomorrow, because for some reason stackoverflow does not allow me to do so right now without waiting 3 hours. :rolleyes:
– Tobias Hermann
Nov 23 '18 at 17:51
add a comment |
First, let's run a different example:
signature: inspect.Signature = inspect.signature(Example)
print(signature)
print(Example.__annotations__)
This prints:
(a: str)
OrderedDict([('a', <class 'str'>)])
So far so good, we have or Signature and our __anotations__ as we expected.
Now let's do the same for the second example, it prints:
(a: 'str')
OrderedDict([('a', ForwardRef('str'))])
So you're not getting the same Signature here. One gives you the actual class and the other a typing.ForwardRef to the class.
answered Nov 22 '18 at 22:53
yorodmyorodm
2,247717
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
The point of using PEP 536 is to not evaluate the annotations unless needed. The signature merely reports on the annotations.
If for your purposes you need to have the annotations resolved, you have to do so yourself. PEP 536 tells documents how you do this:
For code that uses type hints, the
typing.get_type_hints(obj, globalns=None, localns=None)function correctly evaluates expressions back from its string form.
[...]
For code which uses annotations for other purposes, a regular eval(ann, globals, locals) call is enough to resolve the annotation.
You could even use the typing.get_type_hints() function to assign back to __annotations__ before getting the signature:
import typing
Example.__new__.__annotations__ = typing.get_type_hints(Example.__new__)
signature: inspect.Signature = inspect.signature(Example)
Doing this is safe even if from __future__ import annotations had not been used.
answered Nov 22 '18 at 23:38
Martijn Pieters♦Martijn Pieters
714k13724952307
Perfect. Thanks. I'll award the bounty tomorrow, because for some reason stackoverflow does not allow me to do so right now without waiting 3 hours. :rolleyes:
– Tobias Hermann
Nov 23 '18 at 17:51
add a comment |
The point of using PEP 536 is to not evaluate the annotations unless needed. The signature merely reports on the annotations.
If for your purposes you need to have the annotations resolved, you have to do so yourself. PEP 536 tells documents how you do this:
For code that uses type hints, the
typing.get_type_hints(obj, globalns=None, localns=None)function correctly evaluates expressions back from its string form.
[...]
For code which uses annotations for other purposes, a regular eval(ann, globals, locals) call is enough to resolve the annotation.
You could even use the typing.get_type_hints() function to assign back to __annotations__ before getting the signature:
import typing
Example.__new__.__annotations__ = typing.get_type_hints(Example.__new__)
signature: inspect.Signature = inspect.signature(Example)
Doing this is safe even if from __future__ import annotations had not been used.
answered Nov 22 '18 at 23:38
Martijn Pieters♦Martijn Pieters
714k13724952307
Perfect. Thanks. I'll award the bounty tomorrow, because for some reason stackoverflow does not allow me to do so right now without waiting 3 hours. :rolleyes:
– Tobias Hermann
Nov 23 '18 at 17:51
add a comment |
The point of using PEP 536 is to not evaluate the annotations unless needed. The signature merely reports on the annotations.
If for your purposes you need to have the annotations resolved, you have to do so yourself. PEP 536 tells documents how you do this:
For code that uses type hints, the
typing.get_type_hints(obj, globalns=None, localns=None)function correctly evaluates expressions back from its string form.
[...]
For code which uses annotations for other purposes, a regular eval(ann, globals, locals) call is enough to resolve the annotation.
You could even use the typing.get_type_hints() function to assign back to __annotations__ before getting the signature:
import typing
Example.__new__.__annotations__ = typing.get_type_hints(Example.__new__)
signature: inspect.Signature = inspect.signature(Example)
Doing this is safe even if from __future__ import annotations had not been used.
answered Nov 22 '18 at 23:38
Martijn Pieters♦Martijn Pieters
714k13724952307
The point of using PEP 536 is to not evaluate the annotations unless needed. The signature merely reports on the annotations.
If for your purposes you need to have the annotations resolved, you have to do so yourself. PEP 536 tells documents how you do this:
For code that uses type hints, the
typing.get_type_hints(obj, globalns=None, localns=None)function correctly evaluates expressions back from its string form.
[...]
For code which uses annotations for other purposes, a regular eval(ann, globals, locals) call is enough to resolve the annotation.
You could even use the typing.get_type_hints() function to assign back to __annotations__ before getting the signature:
import typing
Example.__new__.__annotations__ = typing.get_type_hints(Example.__new__)
signature: inspect.Signature = inspect.signature(Example)
Doing this is safe even if from __future__ import annotations had not been used.
answered Nov 22 '18 at 23:38
Martijn Pieters♦Martijn Pieters
714k13724952307
answered Nov 22 '18 at 23:38
Martijn Pieters♦Martijn Pieters
714k13724952307
answered Nov 22 '18 at 23:38
Martijn Pieters♦Martijn Pieters
714k13724952307
answered Nov 22 '18 at 23:38
Martijn Pieters♦Martijn Pieters
714k13724952307
714k13724952307
Perfect. Thanks. I'll award the bounty tomorrow, because for some reason stackoverflow does not allow me to do so right now without waiting 3 hours. :rolleyes:
– Tobias Hermann
Nov 23 '18 at 17:51
add a comment |
Perfect. Thanks. I'll award the bounty tomorrow, because for some reason stackoverflow does not allow me to do so right now without waiting 3 hours. :rolleyes:
– Tobias Hermann
Nov 23 '18 at 17:51
Perfect. Thanks. I'll award the bounty tomorrow, because for some reason stackoverflow does not allow me to do so right now without waiting 3 hours. :rolleyes:
– Tobias Hermann
Nov 23 '18 at 17:51
Perfect. Thanks. I'll award the bounty tomorrow, because for some reason stackoverflow does not allow me to do so right now without waiting 3 hours. :rolleyes:
– Tobias Hermann
Nov 23 '18 at 17:51
add a comment |
First, let's run a different example:
signature: inspect.Signature = inspect.signature(Example)
print(signature)
print(Example.__annotations__)
This prints:
(a: str)
OrderedDict([('a', <class 'str'>)])
So far so good, we have or Signature and our __anotations__ as we expected.
Now let's do the same for the second example, it prints:
(a: 'str')
OrderedDict([('a', ForwardRef('str'))])
So you're not getting the same Signature here. One gives you the actual class and the other a typing.ForwardRef to the class.
answered Nov 22 '18 at 22:53
yorodmyorodm
2,247717
add a comment |
First, let's run a different example:
signature: inspect.Signature = inspect.signature(Example)
print(signature)
print(Example.__annotations__)
This prints:
(a: str)
OrderedDict([('a', <class 'str'>)])
So far so good, we have or Signature and our __anotations__ as we expected.
Now let's do the same for the second example, it prints:
(a: 'str')
OrderedDict([('a', ForwardRef('str'))])
So you're not getting the same Signature here. One gives you the actual class and the other a typing.ForwardRef to the class.
answered Nov 22 '18 at 22:53
yorodmyorodm
2,247717
add a comment |
First, let's run a different example:
signature: inspect.Signature = inspect.signature(Example)
print(signature)
print(Example.__annotations__)
This prints:
(a: str)
OrderedDict([('a', <class 'str'>)])
So far so good, we have or Signature and our __anotations__ as we expected.
Now let's do the same for the second example, it prints:
(a: 'str')
OrderedDict([('a', ForwardRef('str'))])
So you're not getting the same Signature here. One gives you the actual class and the other a typing.ForwardRef to the class.
answered Nov 22 '18 at 22:53
yorodmyorodm
2,247717
First, let's run a different example:
signature: inspect.Signature = inspect.signature(Example)
print(signature)
print(Example.__annotations__)
This prints:
(a: str)
OrderedDict([('a', <class 'str'>)])
So far so good, we have or Signature and our __anotations__ as we expected.
Now let's do the same for the second example, it prints:
(a: 'str')
OrderedDict([('a', ForwardRef('str'))])
So you're not getting the same Signature here. One gives you the actual class and the other a typing.ForwardRef to the class.
answered Nov 22 '18 at 22:53
yorodmyorodm
2,247717
answered Nov 22 '18 at 22:53
yorodmyorodm
2,247717
answered Nov 22 '18 at 22:53
yorodmyorodm
2,247717
answered Nov 22 '18 at 22:53
yorodmyorodm
2,247717
2,247717
add a comment |
add a comment |
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The whole point of that PEP is to not get the same object... You'll have to evaluate the string using
execor the like.– Bakuriu
Nov 22 '18 at 22:59