How to Loop: Looping Techniques¶

Lists and Sequences¶

Looping through a sequence¶

for item in ['This', 'class', 'is', 'awesome']:
    print(item)

This
class
is
awesome

Loop through a sequence using `enumerate()`¶

enumerate(['This', 'class', 'is', 'awesome'])

<enumerate at 0x7f8a4df1d480>

list(enumerate(['This', 'class', 'is', 'awesome']))

[(0, 'This'), (1, 'class'), (2, 'is'), (3, 'awesome')]

list(enumerate(['This', 'class', 'is', 'awesome'], start=1))

[(1, 'This'), (2, 'class'), (3, 'is'), (4, 'awesome')]

for iterator, value in enumerate(['This', 'class', 'is', 'awesome']):
    print(iterator, value)

This
class
is
awesome

Loop through a sequence in reverse using `reversed()`¶

for item in reversed(['This', 'class', 'is', 'awesome']):
    print(item)

awesome
is
class
This

Looping through multiple sequences using `zip()`¶

questions = ['sex', 'name', 'shape', 'hello']
answers = ['Male', 'Pau', 'Orange in shape']

for question, answer in zip(questions, answers):
    print('What is your ' + str(question) + '?')
    print('I am ' + str(answer))
    print()

What is your sex?
I am Male

What is your name?
I am Pau

What is your shape?
I am Orange in shape

dict(zip(questions, answers))

{'sex': 'Male', 'name': 'Pau', 'shape': 'Orange in shape'}

Dictionaries¶

Looping though dictionary using `items()`¶

contact = {
    'Ram Kasula': 9840298755,
    'Anu Pau': 98651201503,
    'Kade Hade': 9863331239
}

for name, number in contact.items():
    print(name, number)

Ram Kasula 9840298755
Anu Pau 98651201503
Kade Hade 9863331239

Looping though dictionary using `iteritems()`¶

This is depreciated in Python 3

Exercise¶

Print below pattern using nested loop:
```
* 
* * 
* * * 
* * * * 
* * * * * 
```

Print below pattern:

Print below pattern using nested loop:

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

Print below pattern using loop:

Calculate the individual expense by an individual, total expense and payable amount for each member from below data structures using loop:

expenses = {
    'Eliza': {
        'Dahi': 280,
        'PaniPuri': 120,
        'Bara': 160,
        'Kulfi': 200,
        'Pau': 50,
    },
    'Binay': {
        'Water': 30,
    },
    'Kshitiz': {
        'Chocolate': 90,
    },
    'Sajal': {
        'Coffee':500,
    },
}

Create a dictionary of cubes upto number 10 using loop.
Convert the above expenses dictionary keys to list using loop

'''
Print below pattern using nested loop:

  * 
  * * 
  * * * 
  * * * * 
  * * * * *
'''
for num in range(1,6):
    print('* ' * num)

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

'''
Print below pattern:

  1
  22
  333
  4444
  55555
  666666
  7777777
  88888888
  999999999
'''
for num in range(1,10):
    print(str(num) * num)

'''
Print below pattern using nested loop:

  * 
  * * 
  * * * 
  * * * * 
  * * * * * 
  * * * * 
  * * * 
  * * 
  *
'''
maxStar = 5
for i in range(1, maxStar + 1):
    print('* ' * i)
for i in range(maxStar - 1, 0, -1):
    print('* ' * i)

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

'''
Print below pattern using loop:

   *                                                                      
   *                                                                      
   *                                                                      
   *                                                                      
   *                                                                      
   *                                                                      
   *****
'''
for i in range(1,8):
    if (i == max(range(1,8))):
        print('*' * 5)
    else:
        print('*')

*
*
*
*
*
*
*****

'''
Calculate the individual expense by an individual, total expense and payable amount for each member from below data structures using loop:

  expenses = {
      'Eliza': {
          'Dahi': 280,
          'PaniPuri': 120,
          'Bara': 160,
          'Kulfi': 200,
          'Pau': 50,
      },
      'Binay': {
          'Water': 30,
      },
      'Kshitiz': {
          'Chocolate': 90,
      },
      'Sajal': {
          'Coffee':500,
      },
  }
'''
expenses = {
  'Eliza': {
      'Dahi': 280,
      'PaniPuri': 120,
      'Bara': 160,
      'Kulfi': 200,
      'Pau': 50,
  },
  'Binay': {
      'Water': 30,
  },
  'Kshitiz': {
      'Chocolate': 90,
  },
  'Sajal': {
      'Coffee':500,
  },
}

total_expense = 0
indvExpense = {}

for item in expenses:
    indvExpense[item] = sum(expenses[item].values())
print('Individual expense : ' + str(indvExpense))
print('Total expense :' + str(sum(indvExpense.values())))
payableAmount = sum(indvExpense.values())/len(indvExpense)
print('Payable Amount : ')

for item in indvExpense:
    print(item + '->' + str(indvExpense[item]-payableAmount))

Individual expense : {'Eliza': 810, 'Binay': 30, 'Kshitiz': 90, 'Sajal': 500}
Total expense :1430
Payable Amount : 
Eliza->452.5
Binay->-327.5
Kshitiz->-267.5
Sajal->142.5

#Create a dictionary of cubes upto number 10 using loop.
dictCubes = {}
for i in range(1,11):
    dictCubes[i]=i**3
print(dictCubes)

{1: 1, 2: 8, 3: 27, 4: 64, 5: 125, 6: 216, 7: 343, 8: 512, 9: 729, 10: 1000}

#Convert the above expenses dictionary keys to list using loop
listKeys = []
for item in expenses:
    listKeys.append(item)
print(listKeys)

['Eliza', 'Binay', 'Kshitiz', 'Sajal']

Data Structures Modules