Looping in Python

Loops are an essential part of programming language.
They are used for iteration over data types such as strings, list, tuples, sets and dictionaries.

For Loops iteration over strings.

string = "Learning Python is easy."
for i in string:
    print(i)
#PYTHON OUTPUT
P
y
t
h
o
n

i
s

e
a
s
y
.

Looping through lists, tuple, sets and dictionary.

new_list = [
1,2,3,4,
]

#Looping list
print("Looping through Lists\n")
for i in new_list:
    print(i)


new_tuple = (
'Jake',
'Ronny',
'Peter',
'Sam'
)

print("\n\nLooping through Tuples\n")
for j in new_tuple:
    print(j)

sets = {
"Orange", "mango", "pine-apple"
}

print("\n\nLooping through Sets\n")
for k in sets:
    print(k)


new_dict = {
    "user_id" : 15,
    "username" : "Sam1947",
    "first_name" : "Sam",
    "last_name" : "Paker",
    "profile_pic" : "profile_picture.jpeg",
}

print("\n\nLooping through Keys Dictonary\n")
for k in new_dict:
    print(k)

print("\n\nLooping through Keys and Values Dictonary\n")
for k,v in new_dict.items():
    print("{} : {}".format(k,v))

#PYTHON OUTPUT
Looping through Lists

1
2
3
4


Looping through Tuples

Jake
Ronny
Peter
Sam


Looping through Sets

pine-apple
Orange
mango


Looping through Keys Dictonary

user_id
username
first_name
last_name
profile_pic


Looping through Keys and Values Dictonary

user_id : 15
username : Sam1947
first_name : Sam
last_name : Paker
profile_pic : profile_picture.jpeg

Using `else` statement with for Loop. The `else statement` will be executed after the end of for loop.

new_list = [
'apple', 'grapes'
]

for i in new_list:
    print(i)
else:
    print("Banana")

#PYTHON OUTPUT
apple
grapes
Banana

Using the `break` statement. These are helpful when we want to exit from the loop when certain specify condition matches.

new_list = [
'apple', 'Banana', 'grapes'
]

for i in new_list:
    if(i == "Banana"):
        break
    else:
        print(i)

#PYTHON OUTPUT
apple

Using the ‘continue’ statement. This statement skips execution on certain condition but unlike the `break` statement does not exist loop.

new_list = [
'apple', 'Banana', 'grapes'
]

for i in new_list:
    if(i == "Banana"):
        continue
    else:
        print(i)

#PYTHON OUTPUT
apple
grapes

Python range() method

In simple terms calling range() method with parameters will get us a list of numbers which can be used for iterating over loops.

syntax :

range('start number', 'stop at number', 'number to increament on each loop[Optional parameter]')

Printing list of whole numbers using `range()` method.

for i in range(1,5):
    print(i)

#PYTHON OUTPUT
1
2
3
4    

Printing list of odd numbers using `range()` method.

for i in range(1,10,2):
    print(i)

#PYTHON OUTPUT
1
3
5
7
9

Nested for loop using dictionaries.

d={
    'users' : {
      0 : {
        'username' : 'Rocky1987',
        'fname' : 'Rocky',
        'lname' : 'S',
        'DOB' : '1987-10-05',
        'hobbies' : {
          'swimming',
          'reading books',
          'football',
        }
      },
      1 : {
        'username' : 'Harry12',
        'fname' : 'Harry',
        'lname' : 'J',
        'DOB' : '1995-10-05',
        'hobbies' : {
          'driving cars',
          'mountain climbing',
          'volley ball',
        }
      }
    }
  }
  
  username = "Harry12"
  
  for k,v in d.items():
    if 'users' in k:
      for i,j in  v.items():
        if username == j['username']:
          print('Username exits in dictonary \n {}'.format(j))
          print('\n\n*******************************\n\n')
          print('user hobbies are \n {}'.format(j['hobbies']))
    else:
      print('key not found')

#PYTHON OUTPUT
Username exits in dictonary 
{'username': 'Harry12', 'fname': 'Harry', 'lname': 'J', 'DOB': '1995-10-05', 'hobbies': {'mountain climbing', 'driving cars', 'volley ball'}}


*******************************


user hobbies are 
{'mountain climbing', 'driving cars', 'volley ball'}

While Loop

This loop working is similar to for loop but assigning parameters to vary. Keyword `while` is used before calling condition.

To print even numbers from 1 to 10

k=1
while k<10:
    if k%2==0:
       print(k)
       k+=1

#PYTHON OUTPUT
2
4
6
8

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