In Python, functions are blocks of code that are defined and can be called by name. Functions can take one or more arguments as input and return a value as output. In this article, we will learn about different types of function arguments and return values in Python and how to use them to solve real-world problems.

## Function Arguments

In Python, you can specify one or more arguments when defining a function using the “def” keyword. These arguments are placeholders for the values that will be passed to the function when it is called.

### There are three types of function arguments in Python:

- Required arguments: These are the arguments that must be passed to the function when it is called. If a required argument is not provided, an error will be raised.
- Default arguments: These are the arguments that have a default value specified in the function definition. If the function is called without an argument for that parameter, the default value will be used.
- Keyword arguments: These are the arguments that are specified by name when calling the function. The order of the arguments does not matter when using keyword arguments.

For example, consider the following code:

```
def greet(name, greeting="Hello"):
message = greeting + ", " + name
return message
greeting1 = greet("John")
greeting2 = greet("John", greeting="Hi")
greeting3 = greet(greeting="Hi", name="John")
print(greeting1)
print(greeting2)
print(greeting3)
```

The output of this code will be:

`Hello, John `

`Hi, John `

`Hi, John`

In the above example, we defined a function called “greet” that takes two arguments, “name” and “greeting”, with a default value of “Hello” for the “greeting” argument. When we called the function with only one argument, the default value was used, and the function returned the greeting message “Hello, John”. When we called the function with two arguments, we used keyword arguments to specify the values, and the function returned the greeting message “Hi, John”.

## Function Return Values

In Python, you can use the “return” keyword to specify a value to be returned when a function is called. The “return” keyword can be followed by a value or an expression that will be evaluated and returned.

### There are two types of function return values in Python:

- Single value: This is a value that is returned by the function when it is called. The value can be of any data type, such as a string, integer, or float.
- Multiple values: This is a tuple of values that is returned by the function when it is called. The values can be of any data type, such as strings, integers, or floats.

For example, consider the following code:

```
def add_and_subtract(x, y):
sum = x + y
difference = x - y
return sum, difference
result = add_and_subtract(3, 4)
print(result)
```

The output of this code will be “(7, -1)”.

In the above example, we defined a function called “add_and_subtract” that takes two arguments, “x” and “y”, and returns the sum and difference of these values as a tuple. When we called the function with the arguments “3” and “4”, the values of “x” and “y” were set to “3” and “4” respectively, and the function returned the tuple “(7, -1)”.

## Using Function Arguments and Return Values

Now that we have learned about different types of function arguments and return values in Python, let’s see how we can use them to solve real-world problems.

For example, consider a scenario where you need to create a function that calculates the area and perimeter of a rectangle given its length and width.

To solve this problem, you can use the following function:

```
def calculate_area_and_perimeter(length, width):
area = length * width
perimeter = 2 * (length + width)
return area, perimeter
result = calculate_area_and_perimeter(3, 4)
print(result)
```

The output of this code will be “(12, 14)”.

In the above example, we defined a function called “calculate_area_and_perimeter” that takes two required arguments, “length” and “width”, and returns the area and perimeter of a rectangle as a tuple. When we called the function with the arguments “3” and “4”, the values of “length” and “width” were set to “3” and “4” respectively, and the function returned the tuple “(12, 14)”.

## Conclusion

In this article, we learned about different types of function arguments and return values in Python and how to use them to solve real-world problems. We saw how to define and call functions in Python, how to specify required, default, and keyword arguments, and how to return single and multiple values from a function. With this knowledge, you can create powerful and reusable functions in Python that can save you time and effort when solving complex problems.

## Exercises

Here are some exercises with solutions to help you practice what you just learned:

#### How do you define a function in Python that takes two required arguments and returns the sum and difference of these arguments as a tuple?

To define a function in Python that takes two required arguments and returns the sum and difference of these arguments as a tuple, you can use the “def” keyword followed by the name of the function, two parameters, and a set of parentheses. The code inside the function should calculate the sum and difference of the parameters and return them as a tuple using the “return” keyword. The syntax for defining such a function in Python is as follows:

```
def function_name(parameter1, parameter2):
sum = parameter1 + parameter2
difference = parameter1 - parameter2
return sum, difference
```

For example, consider the following code:

```
def add_and_subtract(x, y):
sum = x + y
difference = x - y
return sum, difference
```

In the above example, we defined a function called “add_and_subtract” that takes two required arguments, “x” and “y”, and returns the sum and difference of these values as a tuple.

#### How do you define a function in Python that takes one required argument and one default argument and returns the product of these arguments?

To define a function in Python that takes one required argument and one default argument and returns the product of these arguments, you can use the “def” keyword followed by the name of the function, two parameters, and a set of parentheses. The second parameter should be assigned a default value. The code inside the function should calculate the product of the parameters and return it using the “return” keyword. The syntax for defining such a function in Python is as follows:

```
def function_name(parameter1, parameter2=default_value):
product = parameter1 * parameter2
return product
```

For example, consider the following code:

```
def multiply(x, y=1):
product = x * y
return product
```

In the above example, we defined a function called “multiply” that takes one required argument, “x”, and one default argument, “y”, with a default value of “1”. The function returns the product of the arguments.

#### How do you define a function in Python that takes two keyword arguments and returns the sum of these arguments?

To define a function in Python that takes two keyword arguments and returns the sum of these arguments, you can use the “def” keyword followed by the name of the function and a set of parentheses that include two parameters. The code inside the function should calculate the sum of the parameters and return it using the “return” keyword. The syntax for defining such a function in Python is as follows:

```
def function_name(parameter1, parameter2):
sum = parameter1 + parameter2
return sum
```

For example, consider the following code:

```
def add(x, y):
sum = x + y
return sum
```

In the above example, we defined a function called “add” that takes two keyword arguments, “x” and “y”, and returns the sum of these arguments.

#### How do you call a function in Python that takes two required arguments and returns the sum and difference of these arguments as a tuple?

To call a function in Python that takes two required arguments and returns the sum and difference of these arguments as a tuple, you can specify the name of the function followed by the arguments inside a set of parentheses. The syntax for calling such a function in Python is as follows:

`function_name(argument1, argument2)`

For example, consider the following code:

```
def add_and_subtract(x, y):
sum = x + y
difference = x - y
return sum, difference
result = add_and_subtract(3, 4)
print(result)
```

The output of this code will be “(7, -1)”.

In the above example, we defined a function called “add_and_subtract” that takes two required arguments, “x” and “y”, and returns the sum and difference of these values as a tuple. When we called the function with the arguments “3” and “4”, the values of “x” and “y” were set to “3” and “4” respectively, and the function returned the tuple “(7, -1)”.

#### How do you call a function in Python that takes one required argument and one default argument and returns the product of these arguments?

To call a function in Python that takes one required argument and one default argument and returns the product of these arguments, you can specify the name of the function followed by the required argument and the keyword argument with its value inside a set of parentheses. If you do not specify a value for the default argument, the default value will be used. The syntax for calling such a function in Python is as follows:

`function_name(argument1, argument2=value)`

For example, consider the following code:

```
def multiply(x, y=1):
product = x * y
return product
result1 = multiply(3, 4)
result2 = multiply(3)
print(result1)
print(result2)
```

The output of this code will be:

```
12
3
```

In the above example, we defined a function called “multiply” that takes one required argument, “x”, and one default argument, “y”, with a default value of “1”. When we called the function with two arguments, the value of “y” was set to “4” and the function returned the product “12”. When we called the function with only one argument, the default value of “y” was used, and the function returned the product “3”.