Suppose I have a class Foo, I want to define a function that receives the class constructor as a parameter:
def bar(class_name):
local_class = None
# TODO: if I call bar(Foo()), I want to get local_class = Foo()
How can I implement the function?
The following bar function will work. Note, the first parameter will be a class itself and not the name of a class, so "class_name", which implies that it's a str, is misleading. args will be a tuple of args to initialize klass objects with, *-unpacked in the calls to klass. You said in a later comment that you wanted to "create multiple independent objects", all of the same class and initialized with the same args, so I've revised my answer to reflect that:
def bar(klass, *args):
# Now you can create multiple independent objects of type klass,
# all initialized with the same args
obj1 = klass(*args)
obj2 = klass(*args)
# ...
# do whatever you have in mind with the objs
Your "local_class" isn't a class at all, but rather an instance of klass, so that's a bad name; and anyway you want several of them.
Assuming Foo objects are initialized with three int arguments, and Baz objects with two strings, you can call bar like so:
bar(Foo, 1, 2, 3)
bar(Baz, 'Yo', 'bro')
etc.
Especially in a dynamically-typed language like Python, reasoning about code is more difficult when variables have misleading names.
When can pass the classname as an argument to your function, and then call class_name(). E.g., if you also want to pass arguments.
class Foo:
def __init__(self, arg1, arg2):
pass
def bar1(class_name):
args = ("val1", "val2")
local_class = class_name(*args)
or
def bar2(class_name):
kwargs = {'arg1':'val1','arg2':'val2'}
local_class = class_name(**kwargs)
You can call the functions like:
one = bar1(Foo)
two = bar2(Foo)
If you really want to call the class from a string read this post. I would suggest you use @Evan Fosmark's solution because use of eval and globals should be avoided
bar(Foo()), you would callbar()function with an instance ofFoo(),can't you directly use that instance?Foo()is not the class constructor. If you want to pass the class, you would passFoo.bar(Foo), thenlocal_class = class_name()would create an instance of Foo.class_nameFootakes parameters? For example,bar(Foo(1,2,3))