Date: 3 Apr 2023
Module : mypy
Installation : pip install mypy
About:
Add type annotations to your Python programs, and use mypy to type check
them. Mypy is essentially a Python linter on steroids, and it can catch
many programming errors by analyzing your program, without actually having
to run it. Mypy has a powerful type system with features such as type
inference, gradual typing, generics and union types.
Sample:
$ pip install mypy
$ cat headlines.py
def headline(text: str, align: bool = True) -> str:
if align:
return f"{text.title()}\n{'-' * len(text)}"
else:
return f" {text.title()} ".center(50, "o")
print(headline("python type checking"))
print(headline("use mypy", align="center"))
$ mypy headlines.py
headlines.py:10: error: Argument "align" to "headline" has incompatible
type "str"; expected "bool"
$ cat headlines.py
def headline(text: str, centered: bool = False):
if not centered:
return f"{text.title()}\n{'-' * len(text)}"
else:
return f" {text.title()} ".center(50, "o")
print(headline("python type checking"))
print(headline("use mypy", centered=True))
$ mypy headlines.py ## No output means no errors
Reference:
https://pypi.org/project/mypy/
https://realpython.com/lessons/type-checking-mypy/
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