getattr()to Assign a Function Into a Variable in Python
globals()to Call a Function From a String in Python
This tutorial will introduce how to call a function using its name in string format in Python.
The use-case for this problem is to assign a function from a module or a class into a variable for whatever use it may have.
getattr() to Assign a Function Into a Variable in Python
getattr() returns a value of an attribute from an object or module. This function has two required arguments, the first argument is the name of the object or module, and the second is a string value that contains the name of the attribute.
The attribute in question may be in the form of a variable, a function, or a subclass.
Let’s say we have a class named
User with the given attributes:
# Filename: user.py class User(): name = 'John' age = 33 def doSomething(): print(name + ' did something.')
Now, we want to store the attribute function
doSomething() into a method and call it. To do this, we’ll use the
from user import User as user doSomething = getattr(user, 'doSomething') doSomething(user)
John did something.
Now, the function
user.doSomething() is wrapped within the variable
doSomething. This way, the object
user doesn’t have to be specified to call the function.
globals() to Call a Function From a String in Python
Another way to call a function from a string is by using the built-in functions
globals. These two functions return a Python dictionary that represents the current symbol table of the given source code.
The difference between the two functions is the namespace. As the names indicate,
locals() returns a dictionary including local variables and
globals() returns a dictionary including local variables. Function names are also returned in the format of the string.
Let’s put these methods into an example. Declare 2 random functions and call it using both built-in functions.
def myFunc(): print('This is a function.') def myFunc2(): print('This is another function.') locals()['myFunc']() globals()['myFunc2']()
This is a function. This is another function.
In summary, to call a function from a string, the functions
globals() are used.
getattr() will require you to know what object or module the function is located in, while
globals() will locate the function within its own scope.