feat: only install typing-extensions dependency when necessary

[nadobando]

Key information

• RFC PR: (leave this empty)
• Related issue(s), if known:
• Area: Parser
• Meet tenets: Yes

Summary

typing-extensions module is a backport for typing hint for old versions of python <= 3.5
in this project many times typing-extensions is imported to use the Literal type hint which is already natively included in python >= 3.8

Motivation

There is no need for this package in Python >= 3.8 and we are currently enforced to install it

Proposal

add if try/except blocks based on the python version

# aws_lambda_powertools/utilities/parser/types.py
import sys

if sys.version_info[0] >= 3 and sys.version_info[1] >= 8:
    from typing import Literal  # noqa: F401
else:
    try:
        from typing_extensions import Literal  # noqa: F401
    except ImportError:
        raise Exception("please install typing-extensions or upgrade to Python >= 3.8")

# aws_lambda_powertools/utilities/parser/models/dynamodb.py
from datetime import date
from typing import Any, Dict, List, Optional

from pydantic import BaseModel

from ..types import Literal


class DynamoDBStreamChangedRecordModel(BaseModel):
    ApproximateCreationDateTime: Optional[date]
    Keys: Dict[str, Dict[str, Any]]
    NewImage: Optional[Dict[str, Any]]
    OldImage: Optional[Dict[str, Any]]
    SequenceNumber: str
    SizeBytes: int
    StreamViewType: Literal["NEW_AND_OLD_IMAGES", "KEYS_ONLY", "NEW_IMAGE", "OLD_IMAGE"]

this is not really a design, it's more a check to wether import typing-extensions or not based on the system python version

in order to use it right instead of importing typing_extensions we can include the dependency in the file types.py and then import that dependency from the types.py as showed in the code blocks

Drawbacks

since this is not a design it's more an improvement of a dependency import I don't see a drawback

Rationale and alternatives

• What is the impact of not doing this?
  The impact of not doing this will be the used of a backport library which is not needed by the interpreter as it has the native implementation

Unresolved questions

no questions

[to-mc]

Thanks @nadobando! I'll have a look at the PR shortly.

[heitorlessa]

Now available in 1.10.2! Thank you very much for this

[hasnain2808]

@nadobando

typing-extensions module is a backport for typing hint for old versions of python <= 3.5

typing-extensions are also needed in say, version 3.8 to use type hints from later versions

Enable experimentation with new type system PEPs before they are accepted and added to the typing module.

https://pypi.org/project/typing-extensions/#description