Day 30 - Types of arguments in Python

Types of Arguments:
Positional Arguments:
The values are assigned to the parameters in the order in which they are passed.

def display(first_name, last_name):
    print("Welcome", first_name, last_name)
display("Lakshmi", "Pritha")

Welcome Lakshmi Pritha

def find_total(l): 
    total = 0 
    for num in l:
        total+=num
    print(total)

marks = [90,56, 78]
find_total(marks)

224

Variable length arguments:

variable length arguments also called as arbitrary arguments.
Same method/function with different number of arguments or with different types of arguments.
Sometimes we don’t know how many arguments will be passed to a function. Python provides ways to handle this with *

def find_total(*l): 
    total = 0 
    for num in l:
        total+=num
    print(total)
mark1 = 100
mark2 = 90
mark3 = 87
find_total(mark1, mark2,mark3)
find_total(45,54)
find_total()

277
99
0

keyword arguments:

keyword arguments by specifying the parameter name followed by an equal sign (=) and the value you want to assign to it.

def display(*marks,name):
    print('Welcome', name)
    print(marks)


display(90,80,name="Lakshmi")
display(80,name="pritha")

Welcome Lakshmi
(90, 80)
Welcome pritha
(80,)

Default Arguments:

Default arguments are parameters that have default values. If the argument is not passed when calling the function, the default value is used.

def login(username, password="admin"):
    print(username, password)


login("abcd", "abcd")
login("pqrs")

abcd abcd
pqrs admin

Keyword variable length arguments:

keyword variable-length arguments allow you to pass a variable number of keyword arguments to a function.

def login(**args):
    print(args)
login(name='raja')

{'name': 'raja'}

def login(**args):
    print(args)
login(name='raja', age=25, city='madurai')

{'name': 'raja', 'age': 25, 'city': 'madurai'}

def modify(l):
    l.append(100)
    print(f'Inside modify, {l}')

l = [10,20,30]
print(f'Outside modify {l}')
modify(l)
print(f'Outside modify2 {l}')

Outside modify [10, 20, 30]
Inside modify, [10, 20, 30, 100]
Outside modify2 [10, 20, 30, 100]

Keyword only arguments:

Keyword-only arguments must be specified by name when calling the function.
The * symbol is used in the function signature to indicate that subsequent arguments are keyword-only.

def add(*, no1, no2):
    return no1+no2

print(add(10,20)) # It returns error
print(add(no1=100,no2=200)) #output:300

Function returning dictionary:

In Python, a function returning a dictionary simply means that the function creates and returns a dictionary object.

The zip() function combines the two lists element-wise, and dict() converts the resulting pairs into a dictionary.

def display(player_names, scores):
    return dict(zip(player_names, scores))

player_names = ['virat', 'rohit']
scores = [100,105]

result = display(player_names, scores)
print(result)

{'virat': 100, 'rohit': 105}

Mutable default arguments:

When you use a list or dictionary as a default argument, it’s initialized only once. If the argument is modified during the function call, the changes persist across future calls.

def add(no, l=[]):
    l.append(no)
    return l

print(add(10))
print(add(20))

[10]
[10, 20]

def add(no, l=None):
    l.append(no)
    return l

print(add(10))
print(add(20))

AttributeError: 'NoneType' object has no attribute 'append'

def add(no, l=None):
    l = []
    l.append(no)
    return l

print(add(10))
print(add(20))

[10]
[20]

Types of variables:

Global variable:

Defined Outside Functions: Global variables are usually declared outside of all functions, at the top level of the code.

no = 10
def f1():
    print(no)

def f2():
    print(no)

f1()
f2()

10
10

Local variable:

Local variables are declared inside functions or blocks of code.

no = 10
def f1():
    no2 = 100
    print(no)
    print(no2)

f1()

10
100

If local and global variable can have same value means the precedence given to the local variable.

amount = 10000
def shopping():
    amount = 1000
    print(amount)

shopping()

1000

The global keyword allows you to modify the global variable amount inside the function.

amount = 10000
def shopping():
    global amount
    print("Total Amount for Trip is",amount)
    amount = 1000
    print("Shopping Amount",amount)

shopping()

Total Amount for Trip is 10000
Shopping Amount 1000

Inner functions:

Inner functions are functions defined inside other functions.
They can access variables from their outer function.

def open_fridge():
    capacity = 165
    print("opening fridge", capacity)
    def take_water():
        capacity = 1
        print("Drink Water", capacity)
    take_water()

open_fridge()

opening fridge 165
Drink Water 1

def open_fridge():
    capacity = 165
    print("opening fridge", capacity)
    def take_water():
        print("Drink Water", capacity)
    take_water()

open_fridge()

opening fridge 165
Drink Water 165

def open_tank():
    tank = 2
    print(f'Inside open_tank {tank}')
    def fill_petrol():
        nonlocal tank # Refers to the variable 'tank' from the enclosing scope
        tank = tank + 3
        print(f'Inside fill_petrol {tank}')
    fill_petrol()

open_tank()

Inside open_tank 2
Inside fill_petrol 5