Overview
Example error:
Traceback (most recent call last):
File "afile.py", line 15, in <module>
print(aFunction(width, height))
TypeError: aFunction() takes 2 positional arguments but 3 were given
Python can report that you are passing one more argument than it appears you are sending.
For example, you are passing two arguments, but Python claims you have passed three.
Initial Steps Overview
Detailed Steps
1) Method inside Python class?
This issue occurs because your method is declared in the context of a Python class.
For example, if your method is bar it is indented inside a class block, like so:
class Foo():
def bar(self, a, b):
print("bar:", self, a, b)
If your method is outside a Python class, then go to step 2.
If your method is inside a Python class, then there are a number of options to consider.
1.1) Instance method
If your method is a straighforward instance method (ie has no decorators such as @staticmethod or @classmethod above the declaration), then it is likely that you forgot to add a first argument to the method signature.
See solution A if this is the case.
1.2) Class method
If your method is a class method (ie has the @classmethod decorator above the declaration), then it is likely that you forgot to add a first argument to the method signature.
See solution B if this is the case.
1.3) Static method
It is also possible that your method should be a static method.
If your method is a utility function that:
doesn’t need an instance of the class to be created to be used, or
doesn’t need to know about the class
then you may want to consider using a static method.
This resolves the problem through the method not receiving an unnecessary first argument (which both 1.1 and 1.2 above, do.
2) Method outside Python class?
If your method is outside a Python class, then it is likely that you have simply passed the wrong number of variables. Here’s some tips that may help:
Check that the function you believe you are calling is actually the function that is being called
Look more closely at the function signature to determine what the correct number of arguments is and whether you are passing that number
Initial Steps Overview
Solutions List
B) Add cls argument to class method
C) Change method to @staticmethod
A) Add self to method
Instance methods receive the instance as their first argument, so you must add this to the list of parameters for your method. By convention, this variable is normally named self. For example, change:
[...]
class Foo():
def bar(a, b):
print("bar:", self, a, b)
to:
[...]
class Foo():
def bar(self, a, b):
print("bar:", self, a, b)
B) Add cls argument to method
Class methods receive a class, so you must add this to the list of parameters for your method. This is so that you can change values within the class or generate a new instance of the given class (factory method). By convention this variable is normally named cls. For example, change:
class Foo():
[...]
@classmethod
def tee(a, b):
print("tee:", cls, a, b)
to:
class Foo():
[...]
@classmethod
def tee(cls, a, b):
print("tee:", cls, a, b)
C) Change method to @staticmethod
This is achieved by adding a decorator to the method, eg changing:
class Foo():
[...]
def qux(a, b):
print("qux:", a, b)
to
class Foo():
[...]
@staticmethod
def qux(a, b):
print("qux:", a, b)
Check Resolution
You should no longer receive the error about being given more positional arguments than your method takes.
