Working with Functions - Revision Notes
CBSE Class 12 Computer Science (Python)
Working with Functions
Revision Notes
- Some important points are as follows:
- A Function is a subprogram that acts on data and often returns a value.
- Functions make program handling easier as only a small part of the program is dealt with at a time, thereby avoiding ambiguity.
- By default, Python names the segment with top-level statements (main program) as __main__.
- A Function is executed in an execution frame.
- The values being passed through a function-call statement are called arguments (or actual parameters or actual arguments)
- The values received in the function definition/header are called parameters (or formal parameters or formal arguments).
- Python supports three types of formal arguments: parameters
- Positional arguments (Required arguments),
- Default arguments and
- Keyword (or named) arguments.
- When the function call statement must match the number and order of arguments as defined in the function definition, this is called the positional argument matching.
- A parameter having default value in the function header is known as a default parameter.
- A default argument can be skipped in the function call statement.
- The default values for parameters are considered only if no value is provided for that parameter in the function call statement.
- Keyword arguments are the named arguments with assigned values being passed in the function call statement.
- A function may or may not return a value.
- A function may also return multiple values that can either be received in a tuple variable or equal number of individual variables.
- A function that returns a non-empty value is a non-void function.
- Functions returning value are also known as fruitful functions.
- A function that does not return a value is known as void function or non-fruitful function.
- A void function internally returns legal empty value None.
- A function in a program can invoke any other function of that program.
- The program part(s) in which a particular piece of code or a data value (e.g., variable) can be accessed is known as Variable Scope.
- In Python, broadly scopes can either be global scope or local scope.
- Python resolves the scope of a name using LEGB rule, i.e. it checks environments in the order: Local, Enclosing, Global and Built-in.
- A local variable having the same name as that of a global variable hides the global variable in its function.
- The global statement tells a function that the mentioned variable is to be used from the global environment.
- The global statement cannot be undone in a code-block i.e., once an identifier is declared global, reverted to local namespace.
- A function can also return multiple values.
- Mutability of arguments/parameter affects the change of value in caller function.