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@ra101
Last active Oct 3, 2021
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A different implementation of constant for python
"""
constant.py: A different implementation of constant for python
"""
class ConstantMeta(type):
"""
Meta Class for Constant, How Constant class would behave
"""
def __new__(cls, clsname, bases, clsdict):
"""
adding __keys__, __values__ fields
and keys(), values() methods
"""
obj = super().__new__(cls, clsname, bases, clsdict)
obj.__force_set__("__values__", [])
obj.__force_set__("__keys__", [])
for key, val in vars(obj).items():
if not key.startswith("__"):
obj.__values__.append(val)
obj.__keys__.append(key)
obj.__force_set__("keys", lambda: obj.__keys__)
obj.__force_set__("values", lambda: obj.__values__)
return obj
def __force_set__(self, name, value):
# A external set method to make sure we can update value in __new__
return super().__setattr__(name, value)
def __setattribute__(self, *args, **kwargs):
# Override set method to make it immutable
pass
def __setattr__(self, *args, **kwargs):
# Override set method to make it immutable
pass
def __setitem__(self, *args, **kwargs):
# Override set method to make it immutable
pass
def __set__(self, *args, **kwargs):
# Override set method to make it immutable
pass
def __getitem__(cls, key):
# adding __getitem__ to make objects "subscriptable"
return getattr(cls, key)
def __iter__(cls):
# In case of for loops
return zip(cls.__keys__, cls.__values__)
class ConstantClass(metaclass=ConstantMeta):
"""
Now this class can be inhereted whenever required to make constants
"""
pass
if __name__ == "__main__":
"""
An Example of how this works
"""
class Links(ConstantClass):
GITHUB = "https://github.com/ra101"
WEB = "https://ra101.github.io/"
LINKS = "dev.ra.101@protonmail.com"
class Author(ConstantClass):
NAME = "〈 RA 〉"
WEB = Links.WEB
LINKS = Links
Links.WEB = 'any_new_value'
print(f"\nLinks.WEB: {Links.WEB}")
print(f"\nAuthor.values(): {Author.values()}")
print(f"\ndict(Author): {dict(Author)}")
print("\nfor key in Author.LINKS.keys()")
for key in Author.LINKS.keys():
print(f'getattr(Author.LINKS, "{key}"): {getattr(Author.LINKS, key)}')
@ra101
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Author

ra101 commented Aug 28, 2021

Output:

Links.WEB: https://ra101.github.io/

Author.values(): ['〈 RA 〉', 'https://ra101.github.io/', <__main__.ConstantClass object at 0x00000293A94768E0>]

dict(Author): {'NAME': '〈 RA 〉', 'WEB': 'https://ra101.github.io/', 'LINKS': <__main__.ConstantClass object at 0x00000293A94768E0>}

for key in Author.LINKS.keys()
getattr(Author.LINKS, "GITHUB"): https://github.com/ra101
getattr(Author.LINKS, "WEB"): https://ra101.github.io/
getattr(Author.LINKS, "EMAIL"): dev.ra.101@protonmail.com

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