BASICS OF FUNCTIONS

Python tutorial · PySpark.in

BASICS OF FUNCTIONS PYTHON

A function in Python is a named block of structured and reusable code that is designed to perform a specific task. Functions help in organizing a program into smaller, manageable units, thereby improving readability, reusability, and maintainability of code.Functions are created using the def keyword and can be executed by calling their name.

Need for Functions

Without functions:

Programs become lengthy and difficult to manage
Same logic must be written repeatedly

With functions:

Code duplication is avoided
Programs become modular
Debugging and testing become easier

General Syntax of a Function

```

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def function_name(parameters):

statements

return value

```

Important Terminologies

Term	Meaning
Function Definition	Writing the function
Function Call	Executing the function
Parameters	Variables in function definition
Arguments	Values passed during function call
Return	Value sent back to caller

Let’s understand each ……

1.FUNCTION DEFINITION

Function definition refers to the process of creating or declaring a function using the def keyword, specifying the function name, parameters, and body.

During function definition, Python does not execute the function, it only stores the function in memory.

Syntax

```

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def function_name(parameters):

statements

``` Example

```

def add(a, b):

c = a + b

return c

```

2. FUNCTION CALL

A function call refers to the process of executing a function by using its name followed by parentheses ().When a function is called, control of the program shifts from the calling statement to the function body.

Syntax

```

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function_name(arguments)

```

Example

```

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result = add(10, 20)

```

Execution Flow

Program encounters function call
Control transfers to function definition
Arguments are assigned to parameters
Function body executes
Control returns to the calling statement

3. PARAMETERS

Parameters are the variables listed in the function definition that receive values from the calling function. They act as placeholders for the data that will be passed during the function call.

Example

```

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def multiply(x, y):

return x * y

```

Here:

x and y are parameters

Characteristics of Parameters

Defined inside parentheses in function definition
Receive values during function call
Local to the function

Note
Parameters exist only inside the function.

4. ARGUMENTS

Arguments are the actual values supplied to a function at the time of function call. They provide the data on which the function operates.

Example

```

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multiply(5, 4)

```

Here:

5 and 4 are arguments

Difference Between Parameters and Arguments

Parameter	Argument
Defined in function definition	Used in function call
Acts as a placeholder	Actual value passed
Variable name	Constant or variable
Local to the function	Exists in calling scope
Receives data	Supplies data
Defined only once	Can change for each call

5.RETURN STATEMENT

The return statement is used to send a value from the function back to the calling statement and terminate the execution of the function. If a function does not use a return statement, it returns None by default.

Syntax

```

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return expression

```

Example

```

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def square(n):

return n * n

result = square(4)

print(result)

```

Key Characteristics of Return

Ends function execution
Can return any data type
Can return multiple values (as tuple)
Transfers control back to caller

Example: Multiple Return Values

```

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def operations(a, b):

return a+b, a-b

x, y = operations(10, 5)

```

COMPLETE FLOW EXAMPLE

```

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def add(a, b): # Function Definition

return a + b # Return statement

result = add(10, 20) # Function Call with arguments

```

BASICS OF FUNCTIONS