functions notes.pdf python functions and opp

FUNCTIONS A function is a block of organized, reusable code that is used to perform a single, related action.  Functions provide better modularity for the applications.  Functions provide a high degree of code reusing.

RULES FOR DEFINING FUNCTION IN PYTHON  Function blocks begin with the keyword def followed by the function name and parentheses ( ( ) ).  Any input parameters or arguments should be placed within these parentheses. We also define parameters inside these parentheses.  The code block within every function starts with a colon (:) and is indented.  The statement return [expression] exits a function, optionally passing back an expression to the caller.  A return statement with no arguments is the same as return None.

Function Syntax The keyword def introduces a function definition. Input Parameter is placed within the parenthesis() and also define parameter inside the parenthesis. Return statement exits a function block. And we can also use return with no argument. The code block within every function starts with a colon(:) .

Passing arguments :-when the user defined function is called ,values are transferred from calling function to called function.These values are called as arguments. 1. Required arguments 2. Keyword arguments 3. Default arguments 4. Variable length arguments PASSING ARGUMENTS

REQUIRED ARGUMENT VALUES VALUES  Required arguments are mandatory for the function call  First the required argument should be listed,then the default argument should be listed.  EXAMPLE: Output: In this code, argument ‘b’ has given a default value. ie(b=10),and a is required argument. When the value of ‘b’ is not passed in function ,then it takes default argument. def sum(a,b=10): return(a+b) print("sum=",sum(10,20)) print("sum=",sum(20)) print("sum=",sum(10)) Sum=30 Sum=30 Sum=20

DEFAULT ARGUMENT VALUES  Default Argument- argument that assumes a default value if a value is not provided in the function call for that argument.  The default value is evaluated only once.  EXAMPLE: Output: In this code, argument ‘b’ has given a default value. ie(b=90) When the value of ‘b’ is not passed in function ,then it takes default argument.

DEFAULT ARGUMENTS  The default value is evaluated only once. This makes a difference when the default is a mutable object such as a list, dictionary, or instances of most classes.  Example:  if we don’t want the default value to be shared between subsequent calls, then  Example : Output: Output:

KEYWORD ARGUMENTS  Keyword arguments are related to the function calls.  Using keyword arguments in a function call, the caller identifies the arguments by the parameter name.  Allows to skip arguments or place them out of order, the Python interpreter use the keywords provided to match the values with parameters.  Example: Output:  Caller identifies the keyword argument by the parameter name.  Calling of the argument Order doesn’t matter .

KEYWORD ARGUMENTS  Example 1: Output: Example 2: Output:

ARBITRARY ARGUMENT LISTS  Variable-Length Arguments: more arguments than we specified while defining the function.  These arguments are also called variable-length arguments .  An asterisk (*) is placed before the variable name that holds the values of all non keyword variable arguments.  This tuple remains empty if no additional arguments are specified during the function call.  Syntax : def function_name([formal_args], *var_args_tuple ): statement 1…… statement 2…… return [expression] This is called arbitrary argument and asterisk sign is placed before the variable name.

ARBITRARY ARGUMENT LISTS  EXAMPLE 1: Output: Output:  EXAMPLE 2:  Any formal parameter which occur after the *args parameter are keyword-only arguments.  If formal parameter are not keyword argument then error occurred. Monika Ranbir Purva Lalit def fun2(*variable,value="Monika"): print(value) for val in variable: print(val) return fun2("Ranbir","Purva","Lalit")

LAMBDA EXPRESSIONS  Small functions can be created with the lambda keyword also known as Anonymous function.  Used wherever functions object are required.  These functions are called anonymous because they are not declared in the standard manner by using the def keyword. .  Syntax :  EXAMPLE: lambda [arg1 [,arg2,.....argn]]:expression Output:  The function returns the multiply of two arguments.  Lambda function is restricted to a single expressions. Anonymous Functions

Returning Statement The return statement is used to return the values from user-defined function to calling statement. Return keyword is used to return values

Returning values Example Description return c Returns c from the function return 100 Returns constant from a function return lst Return thelist that contains values return z,y,z Returns more than one value

Returning M values # A function that returns two results def sum_sub(a, b): c = a + b d = a – b return c, d # get the results from sum_sub() function x, y = sum_sub(10, 5) # display the results print("Result of addition: ", x) print("Result of subtraction: ", y)

Recursive Function A function which calls itself is called recursive function EXAMPLE: def pr(a): if(a>0): print(a) pr(a-1) else: return() pr(5) Output 5 4 3 2 1

Local and Global Variables KEY DIFFERENCE Local variable is declared inside a function whereas Global variable is declared outside the function. Local variables are created when the function has started execution and is lost when the function terminates, on the other hand, Global variable is created as execution starts and is lost when the program ends. Local variable doesn’t provide data sharing whereas Global variable provides data sharing. Local variables are stored on the stack whereas the Global variable are stored on a fixed location decided by the compiler. Parameters passing is required for local variables whereas it is not necessary for a global variable

LOCAL VARIABLE Local Variable is defined as a type of variable declared within programming block or subroutines. It can only be used inside the subroutine or code block in which it is declared. The local variable exists until the block of the function is under execution. After that, it will be destroyed automatically. Example of Local Variable #local variable def funct(): z=10 print("local variable value",z) funct() print("local variable outside value",z)

GLOBAL VARIABLE A Global Variable in the program is a variable defined outside the subroutine or function. It has a global scope means it holds its value throughout the lifetime of the program. Hence, it can be accessed throughout the program by any function defined within the program, unless it is shadowed. EXAMPLE: #global variable z=10 def funct(): print("global variable value",z) funct() print("global variable outside value",z)

DIFFERENCE BETWEEN LOCAL /GLOBAL Parameter Local Global Scope It is declared inside a function. It is declared outside the function. Value If it is not initialized, a garbage value is stored If it is not initialized zero is stored as default. Lifetime It is created when the function starts execution and lost when the functions terminate. It is created before the program's global execution starts and lost when the program terminates. Data sharing Data sharing is not possible as data of the local variable can be accessed by only one function. Data sharing is possible as multiple functions can access the same global variable. Parameters Parameters passing is required for local variables to access the value in other function Parameters passing is not necessary for a global variable as it is visible throughout the program Modification of variable value When the value of the local variable is modified in one function, the changes are not visible in another function. When the value of the global variable is modified in one function changes are visible in the rest of the program. Accessed by Local variables can be accessed with the help of statements, inside a function in which they are declared. You can access global variables by any statement in the program. Memory storage It is stored on the stack unless specified. It is stored on a fixed location decided by the compiler.

USING GLOBAL STATEMENT It is used to declare the variable as global variables,once the variable is declared as global the corresponding variable can be used in any other function #global statement def ff(): global m m=10 print("m value inside function ",m) ff() print("m value outside function ",m)

MODULES A module allows you to logically organize your Python code.  Grouping related code into a module makes the code easier to understand and use.  A module is a Python object with arbitrarily named attributes that you can bind and reference. Simply, a module is a file consisting of Python code.  A module can define functions, classes and variables. A module can also include runnable code.

Create a Module To create a module just save the code you want in a file with the file extension .py: def greeting(name): print("Hello, " + name)

Importing elements of a Module Importing all elements Importing specific elements of a module Example Import the module named mymodule, and call the greeting function: import mymodule mymodule.greeting("John")

Built-in Modules Example Import and use the platform module: import platform x = platform.system() print(x) Using the dir() Function There is a built-in function to list all the function names (or variable names) in a module. The dir() function: Example List all the defined names belonging to the platform module: import platform x = dir(platform) print(x)

functions notes.pdf python functions and opp

More Related Content

What's hot

Similar to functions notes.pdf python functions and opp

Recently uploaded

functions notes.pdf python functions and opp