What Is an Argument in Python?

An argument in Python is a value you pass to a function when you call it.

This helps the function work with real data. For example, a function can greet different people, add different numbers, or print different messages based on the arguments you give it.

A common beginner confusion is the difference between arguments and parameters:

Parameters are the names written in the function definition.
Arguments are the actual values passed into the function call.

def greet(name):
    print("Hello", name)

greet("Sam")

"Sam" is the argument. It is the value passed to the function.

Simple definition

An argument is a value you give to a function when you call it.
The function uses that value while it runs.
Arguments go inside the parentheses after the function name.

For example:

print("Hello")

Here, "Hello" is the argument passed to print().

Argument vs parameter

This difference is important when you start writing your own functions.

A parameter is the variable named in the function definition.
An argument is the actual value passed to that function.
In def greet(name), name is a parameter.
In greet("Sam"), "Sam" is an argument.

Example:

def greet(name):
    print("Hello", name)

greet("Sam")

What each part means:

name is the parameter
"Sam" is the argument

If you want a fuller explanation, see function parameters and arguments in Python and what is a parameter in Python.

Why arguments are useful

Arguments make functions flexible.

They let one function work with different values.
They make code more reusable.
They help avoid repeating similar code.

Example:

def greet(name):
    print("Hello", name)

greet("Sam")
greet("Ava")
greet("Leo")

Output:

Hello Sam
Hello Ava
Hello Leo

The function stays the same. Only the argument changes.

Common types of arguments beginners see

Positional arguments

A positional argument is matched by order.

def add(a, b):
    print(a + b)

add(3, 5)

Output:

Here:

3 is passed to a
5 is passed to b

If you swap the order, the values go into different parameters.

Keyword arguments

A keyword argument is matched by parameter name.

def greet(name, message):
    print(message, name)

greet(name="Sam", message="Hello")

Output:

Hello Sam

Keyword arguments can make code easier to read. Learn more in default and keyword arguments explained.

Default arguments

A parameter can have a default value. If you do not pass an argument for it, Python uses the default.

def greet(name="friend"):
    print("Hello", name)

greet()
greet("Sam")

Output:

Hello friend
Hello Sam

How to read a function call

When you see a function call, read it in this order:

Look at the function name first.
Then look inside the parentheses.
The values inside are the arguments.
A function can have zero, one, or many arguments.

Examples:

print("Hi")
len("apple")
sum([1, 2, 3])

In these calls:

"Hi" is an argument to print()
"apple" is an argument to len()
[1, 2, 3] is an argument to sum()

If you are new to functions, it also helps to read what is a function in Python.

Beginner examples to include

One argument passed to a print-like function

print("Python is fun")

"Python is fun" is the argument.

Two arguments passed to an add function

def add(a, b):
    print(a + b)

add(10, 20)

Output:

10 and 20 are the arguments.

Keyword argument example

def show_user(name, age):
    print(name, age)

show_user(age=25, name="Maya")

Output:

Maya 25

The arguments are still values, but they are passed by parameter name.

Function call with no arguments

def say_hello():
    print("Hello")

say_hello()

This function call has no arguments because nothing is inside the parentheses.

Common mistakes

Beginners often run into these problems:

Mixing up arguments and parameters
Thinking the variable in def is the argument
Passing arguments in the wrong order
Forgetting required arguments when calling a function
Using a keyword name that does not exist in the function definition

Example of a missing argument:

def greet(name):
    print("Hello", name)

greet()

This causes an error because name needs a value.

If you see this problem, read how to fix TypeError: missing required positional argument.

Useful checks while learning:

help(print)
help(len)
print(type("Sam"))
print(len.__defaults__)

These can help you inspect built-in functions and understand what kind of values you are passing.

FAQ

What is the difference between an argument and a parameter in Python?

A parameter is the name in the function definition. An argument is the value passed when calling the function.

Can a function have more than one argument?

Yes. A function can accept multiple arguments if it is defined with multiple parameters.

Can a function have no arguments?

Yes. Some functions are called with empty parentheses.

Are keyword arguments and positional arguments both arguments?

Yes. They are two common ways to pass values to a function.