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
    1. Positional arguments (Required arguments),
    2. Default arguments and
    3. 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.