Is there any way to declare class with name that I have stored in string variable in Python?
class_name = "User"
class [class_name]:
def hello():
return "world"
2 Answers
You can pass a string to type() and get a class back if you use the three-argument form of type.
As the docs say:
With three arguments, return a new type object. This is essentially a dynamic form of the class statement.
Now, whether this is a good solution for your problem, I'll leave up to you...
class_name = "User"
def hello(self):
return self.class_attr + " world"
AClass = type(class_name, (object,), {'class_attr': 'something', 'hello':hello})
a = AClass()
print(a)
# <__main__.User object at 0x7fc0cb29bb10>
print(a.class_attr)
# something
print(a.hello())
# 'something world'
Comments
You can use namedtuple like this:
from collections import namedtuple
class_name = "User"
a = namedtuple(class_name, "attr1, attr2, hello")
print(a) # <class '__main__.User'>
obj = a(1, 2, lambda: print("hello world!"))
print(obj) # User(attr1=1, attr2=2, hello=<function <lambda> at 0x00000241E2FA4B88>)
obj.hello() # hello world!
4 Comments
Mark
Some important differences between an object and a tuple will become apparent when you try to either add a method (like the OP's
hello()) or change one of the attributes.
ThunderPhoenix
@MarkMeyer I agree it is somehow limited than classes. However, we can easily implement methods: see my update. I added
hello method.Mark
You've added a static function, not a method. A method would allow you to use the state of the object — for example to print one of the attributes or to sum the attributes, etc...
ThunderPhoenix
@MarkMeyer Yes I agree, but we can emulate a method by defining a lambda function with 1 parameter. And whenever we call it, we give to it the object. It is not like real class, but it might work.
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