Python Lists Advanced

ll = [10, 20, 30, 40, 50]

# insert, remove, pop
ll.remove(20) #[10, 30, 40, 50]
ll.pop() # #[10, 30, 40]

ll = [1, 3, 5, 'seven']
ll.insert(0, 2) 
print(ll) # [2, 1, 3, 5, 'seven']

ll.pop(2) # pops 2nd index element
print(ll) # [2, 1, 5, 'seven']

ll.pop() # takes out last item
print(ll) # [2, 1, 5]

# Slice
gg = [1, 3, 5, 'seven', 'eight', 'nine', [10, 20,]]
print(gg[1:4])  # [3, 5, 'seven']
print(gg[3:])  # ['seven', 'eight', 'nine', [10, 20]]
print(gg[:3])  # [1, 3, 5]
print(gg[:])  # [1, 3, 5, 'seven', 'eight', 'nine', [10, 20]]

print(gg[-1:]) # [[10, 20]]
print(gg[:-1]) # [1, 3, 5, 'seven', 'eight', 'nine']

print(gg[-3:-1]) # ['eight', 'nine']

# list[start:stop:step]
print(gg[0:7:2]) # [1, 5, 'eight', [10, 20]]

ff = [1, 3, 5, 'seven', 'eight', 'nine']
print(ff) #[1, 3, 5, 'seven', 'eight', 'nine']
ff[2:2] = ['test']
print(ff) # [1, 3, 'test', 5, 'seven', 'eight', 'nine']
ff[1:3] = []
print(ff) # [1, 5, 'seven', 'eight', 'nine']

del ff[::2] # Delete even numbred indeces
print(ff)  # [5, 'eight']

# Concatenate
kk = [1, 2, 3, 4] # [1, 2, 3, 4]
kk += 'ab' # since string, it takes as two elements
print(kk) # [1, 2, 3, 4, 'a', 'b']

kk += ['c', 'd']
print(kk) # [1, 2, 3, 4, 'a', 'b', 'c', 'd']

kk.extend(['e', 'f'])
print(kk) # [1, 2, 3, 4, 'a', 'b', 'c', 'd', 'e', 'f']

# List Vs Array
# Array has homogenous elements
# Python arrays are just wrappers for C language
import array
# type: 'd' (float), initializer list: [1, 2, 3]
newArray = array.array('i', [1, 2, 3])
print(newArray) # array('i', [1, 2, 3])

Python remove all occurrences a given element from the list

#Method1
#Use the same list (don't use another list)
lista = [10, 10, 20, 10, 30, 10, 40, 10, 50]
print(lista)
#o/p: [20, 30, 40, 50]

#Note:
#Every time when you remove item, list index changes

n = 10 #element to remove

print('------Method1-----')
i = 0
listlen = len(lista)
while(i < listlen):
  if lista[i] == n:
    lista.remove(n)
    listlen -= 1
    continue
  i += 1

print(lista)   #[20, 30, 40, 50]


#Method2
print('-----Method2-----')
#Remove element and copy to another list
lista = [10, 10, 20, 10, 30, 10, 40, 10, 50]
listb = list(filter(lambda x: x != 10, lista))
print(listb)   #[20, 30, 40, 50]
listb = [i for i in lista if i != 10]
print(listb)   #[20, 30, 40, 50]

Compare List Vs List Comprehension, timeit

import timeit

# timeit.timeit(stmt, setup, timer, number)
# stmt   - which is the statement you want to measure it defaults to 'pass'.
# setup  - which is the code that you run before running the stmt; it defaults to 'pass'. We generally use this to import the required modules for our code.
# number - number of executions you like to run the stmt.

# List Comprehension

lst = [3, 2, 41, 3, 34, 99]

print(lst)

# If Condition alone - keep after the For loop

print([number for number in lst if number % 2 != 0])

# If-Else Condition - keep before For loop

print([number if number % 2 != 0 else -1 for number in lst])

#List Vs List Comprehension
#Ref: https://stackoverflow.com/questions/16341775/what-is-the-advantage-of-a-list-comprehension-over-a-for-loop
#List comprehensions are more compact and faster than an explicit for loop building a list:
#This is because calling .append() on a list causes the list object to grow (in chunks) to make space for new elements individually, while the list comprehension gathers all elements first before creating the list to fit the elements in one go:

def for_loop_test():
    result = []
    for elem in iter_var:
        result.append(elem)
    return result

def list_comprehension_test():
    return [elem for elem in iter_var]

if __name__ == '__main__':
iter_var = range(1000)
print timeit.timeit('f()', 'from __main__ import for_loop_test as f', number=10000)
print timeit.timeit('f()', 'from __main__ import list_comprehension_test as f', number=10000)


"""
Output:
1.41242463295
0.474811508482
"""'

Python compare lists

#Comapre lists

student1_scores = [61, 73, 84, 90, 85, 45]
student2_scores = [40, 37, 45, 87, 99, 54]

#set - will change the order
print list(set(student1_scores)) #[73, 45, 84, 85, 90, 61]
print list(set(student2_scores)) #[99, 37, 40, 45, 54, 87]

#Commom elements in two lists
print list(set(student1_scores) & set(student2_scores)) #[45]

#Commom elements in two lists
print list(set(student1_scores).intersection(set(student2_scores))) #[45]

#Union of two lists
print list(set(student1_scores).union(set(student2_scores))) 
#[99, 37, 40, 73, 45, 84, 85, 54, 87, 90, 61]

#Commom elements in two lists - using list comprehension
print [i for i in student1_scores if i in student2_scores] #[45]

#compare common elements with for the same subject (same index)
student1_scores = [61, 73, 84, 90, 85, 45]
student2_scores = [40, 37, 45, 90, 99, 54]

print [i for i, j in zip(student1_scores, student2_scores) if i == j] #[90]

Learning lists - all operations

#!/usr/local/bin/python2.7

'''
    File name: list_all_operations.py
    Author: Prabhath Kota
    Date: June 22, 2018
    Python Version: 2.7
'''

freedom_fighters = ["Lala Lajipati Rai", "Dadabhai Naoroji", "Rajendra Prasad", "Sarojini Naidu", "Dadabhai Naoroji", "Lal Bahadur Shastri"]
print freedom_fighters
#['Lala Lajipati Rai', 'Dadabhai Naoroji', 'Rajendra Prasad', 'Sarojini Naidu', 'Dadabhai Naoroji', 'Lal Bahadur Shastri']

print '---------------index---------------'
print freedom_fighters[0]
print freedom_fighters[-1]
print freedom_fighters[2:]
print freedom_fighters[:-1]
print freedom_fighters[2:4]

#Lala Lajipati Rai
#Lal Bahadur Shastri
#['Rajendra Prasad', 'Sarojini Naidu', 'Dadabhai Naoroji', 'Lal Bahadur Shastri']
#['Lala Lajipati Rai', 'Dadabhai Naoroji', 'Rajendra Prasad', 'Sarojini Naidu', 'Dadabhai Naoroji']
#['Rajendra Prasad', 'Sarojini Naidu']

print '---------------insert in index---------------'
freedom_fighters[2] = 'Subhash Chandra Bose'
print freedom_fighters
#['Lala Lajipati Rai', 'Dadabhai Naoroji', 'Subhash Chandra Bose', 'Sarojini Naidu', 'Dadabhai Naoroji', 'Lal Bahadur Shastri']

print '---------------Add Element append vs extend---------------'
print freedom_fighters
#Append - appends as a single item
freedom_fighters.append('Subhash Chandra Bose')
print freedom_fighters
freedom_fighters.pop()
freedom_fighters.append(['Subhash Chandra Bose', 'Lal Bahadur Shastri'])
print freedom_fighters
freedom_fighters.pop()
#Extend - it adds multiple values
freedom_fighters.extend(['Subhash Chandra Bose', 'Lal Bahadur Shastri'])
print freedom_fighters
freedom_fighters.pop()
freedom_fighters.pop()
print freedom_fighters

#['Lala Lajipati Rai', 'Dadabhai Naoroji', 'Subhash Chandra Bose', 'Sarojini Naidu', 'Dadabhai Naoroji', 'Lal Bahadur Shastri']
#['Lala Lajipati Rai', 'Dadabhai Naoroji', 'Subhash Chandra Bose', 'Sarojini Naidu', 'Dadabhai Naoroji', 'Lal Bahadur Shastri', 'Subhash Chandra Bose', ['Subhash Chandra Bose', 'Lal Bahadur Shastri']]
#['Lala Lajipati Rai', 'Dadabhai Naoroji', 'Subhash Chandra Bose', 'Sarojini Naidu', 'Dadabhai Naoroji', 'Lal Bahadur Shastri', 'Subhash Chandra Bose', 'Subhash Chandra Bose', 'Lal Bahadur Shastri']
#['Lala Lajipati Rai', 'Dadabhai Naoroji', 'Subhash Chandra Bose', 'Sarojini Naidu', 'Dadabhai Naoroji', 'Lal Bahadur Shastri']

print '---------------Remove Element by value---------------'
print freedom_fighters
freedom_fighters.remove('Subhash Chandra Bose')
print freedom_fighters

#['Lala Lajipati Rai', 'Dadabhai Naoroji', 'Subhash Chandra Bose', 'Sarojini Naidu', 'Dadabhai Naoroji', 'Lal Bahadur Shastri']
#['Lala Lajipati Rai', 'Dadabhai Naoroji', 'Sarojini Naidu', 'Dadabhai Naoroji', 'Lal Bahadur Shastri']

print '-----------delete by index---------------------'
print freedom_fighters
del freedom_fighters[-1] #removes index element
del freedom_fighters[1] #removes index element
print freedom_fighters

#['Lala Lajipati Rai', 'Dadabhai Naoroji', 'Sarojini Naidu', 'Dadabhai Naoroji', 'Lal Bahadur Shastri']
#['Lala Lajipati Rai', 'Sarojini Naidu', 'Dadabhai Naoroji']

print '---------------By Ref---------------'
print freedom_fighters

#copy by Reference
freedom_fighters_1 = freedom_fighters
freedom_fighters_1.append('Bhagat Singh')
print freedom_fighters
print freedom_fighters_1

#['Lala Lajipati Rai', 'Sarojini Naidu', 'Dadabhai Naoroji']
#['Lala Lajipati Rai', 'Sarojini Naidu', 'Dadabhai Naoroji', 'Bhagat Singh']
#['Lala Lajipati Rai', 'Sarojini Naidu', 'Dadabhai Naoroji', 'Bhagat Singh']

print '---------------By Value -----------'
#copy by value
freedom_fighters_2 = freedom_fighters[:]
freedom_fighters_2.append('Sardar Vallabhbhai Patel')
print freedom_fighters
print freedom_fighters_2

#['Lala Lajipati Rai', 'Sarojini Naidu', 'Dadabhai Naoroji', 'Bhagat Singh']
#['Lala Lajipati Rai', 'Sarojini Naidu', 'Dadabhai Naoroji', 'Bhagat Singh', 'Sardar Vallabhbhai Patel']

print '---------------List Comprehension ---------------'

#This gives list
print [i + ' - India Salutes you' for i in freedom_fighters]

#tuple - gives generator object
generator_obj = (i + ' - India Salutes you' for i in freedom_fighters)
print generator_obj
for each in generator_obj:
print each

#['Lala Lajipati Rai - India Salutes you', 'Sarojini Naidu - India Salutes you', 'Dadabhai Naoroji - India Salutes you', 'Bhagat Singh - India Salutes you']
#<generator object <genexpr> at 0x0000000001EB41B0>
#Lala Lajipati Rai - India Salutes you
#Sarojini Naidu - India Salutes you
#Dadabhai Naoroji - India Salutes you
#Bhagat Singh - India Salutes you

print '---------------Sorted()---------------'
print freedom_fighters
print sorted(freedom_fighters)
print freedom_fighters

#['Lala Lajipati Rai', 'Sarojini Naidu', 'Dadabhai Naoroji', 'Bhagat Singh']
#['Bhagat Singh', 'Dadabhai Naoroji', 'Lala Lajipati Rai', 'Sarojini Naidu']
#['Lala Lajipati Rai', 'Sarojini Naidu', 'Dadabhai Naoroji', 'Bhagat Singh']

print '---------------list.reverse() ---------------'
print freedom_fighters
print freedom_fighters.reverse() #Returns None but reverse itself
print freedom_fighters

#['Lala Lajipati Rai', 'Sarojini Naidu', 'Dadabhai Naoroji', 'Bhagat Singh']
#None
#['Bhagat Singh', 'Dadabhai Naoroji', 'Sarojini Naidu', 'Lala Lajipati Rai']

print '---------------list.sort() ---------------'
print freedom_fighters
print freedom_fighters.sort() #Returns None but sorts itself
print freedom_fighters

#['Bhagat Singh', 'Dadabhai Naoroji', 'Sarojini Naidu', 'Lala Lajipati Rai']
#None
#['Bhagat Singh', 'Dadabhai Naoroji', 'Lala Lajipati Rai', 'Sarojini Naidu']

print '---------------multiply---------------'
freedom_fighters2 = freedom_fighters * 2
print freedom_fighters2
#['Bhagat Singh', 'Dadabhai Naoroji', 'Lala Lajipati Rai', 'Sarojini Naidu', 'Bhagat Singh', 'Dadabhai Naoroji', 'Lala Lajipati Rai', 'Sarojini Naidu']

print '---------------check if item exits---------------'
print freedom_fighters
print 'Bhagat Singh' in freedom_fighters
print 'Sardar Vallabhbhai Patel' in freedom_fighters

#['Bhagat Singh', 'Dadabhai Naoroji', 'Lala Lajipati Rai', 'Sarojini Naidu']
#True
#False

print '---------------Remove Duplicates---------------'
print freedom_fighters
freedom_fighters.append('Mahatma Gandhi')
freedom_fighters.append('Mahatma Gandhi')
print freedom_fighters
freedom_fighters_no_dup = []
[freedom_fighters_no_dup.append(x) for x in freedom_fighters if x not in freedom_fighters_no_dup]
print freedom_fighters_no_dup
print list(set(freedom_fighters)) #set - unordered collection data type, this kills the original order

#['Bhagat Singh', 'Dadabhai Naoroji', 'Lala Lajipati Rai', 'Sarojini Naidu']
#['Bhagat Singh', 'Dadabhai Naoroji', 'Lala Lajipati Rai', 'Sarojini Naidu', 'Mahatma Gandhi', 'Mahatma Gandhi']
#['Bhagat Singh', 'Dadabhai Naoroji', 'Lala Lajipati Rai', 'Sarojini Naidu', 'Mahatma Gandhi']
#['Mahatma Gandhi', 'Bhagat Singh', 'Lala Lajipati Rai', 'Dadabhai Naoroji', 'Sarojini Naidu']

print '---------------Convert to tuple---------------'
print freedom_fighters
print tuple(freedom_fighters)
print list(tuple(freedom_fighters))

#['Bhagat Singh', 'Dadabhai Naoroji', 'Lala Lajipati Rai', 'Sarojini Naidu', 'Mahatma Gandhi', 'Mahatma Gandhi']
#('Bhagat Singh', 'Dadabhai Naoroji', 'Lala Lajipati Rai', 'Sarojini Naidu', 'Mahatma Gandhi', 'Mahatma Gandhi')
#['Bhagat Singh', 'Dadabhai Naoroji', 'Lala Lajipati Rai', 'Sarojini Naidu', 'Mahatma Gandhi', 'Mahatma Gandhi']

print '---------------length of array---------------'
print freedom_fighters
print len(freedom_fighters) 

#['Bhagat Singh', 'Dadabhai Naoroji', 'Lala Lajipati Rai', 'Sarojini Naidu', 'Mahatma Gandhi', 'Mahatma Gandhi']
#6

print '---------------Find count of Element---------------'
freedom_fighters.append('Bhagat Singh')
print freedom_fighters
print freedom_fighters.count('Bhagat Singh')

#['Bhagat Singh', 'Dadabhai Naoroji', 'Lala Lajipati Rai', 'Sarojini Naidu', 'Mahatma Gandhi', 'Mahatma Gandhi', 'Bhagat Singh']
#2

print '---------------Pop---------------'
#pop() method removes and returns the last item if index is not provided
print freedom_fighters
freedom_fighters.pop()
print freedom_fighters

#['Bhagat Singh', 'Dadabhai Naoroji', 'Lala Lajipati Rai', 'Sarojini Naidu', 'Mahatma Gandhi', 'Mahatma Gandhi', 'Bhagat Singh']
#['Bhagat Singh', 'Dadabhai Naoroji', 'Lala Lajipati Rai', 'Sarojini Naidu', 'Mahatma Gandhi', 'Mahatma Gandhi']

print '---------------Insert---------------'
#When you insert(-3, 0) you are inserting 0 before index -3. 
#When it says "before" it has nothing to do with the direction of travel.
print freedom_fighters
freedom_fighters.insert(0,'Sarojini Naidu')
freedom_fighters.insert(len(freedom_fighters),'Sarojini Naidu')
print freedom_fighters
freedom_fighters.insert(-1,'Bhagat Singh')
print freedom_fighters
del freedom_fighters[0]
freedom_fighters.pop()
freedom_fighters.pop()
print freedom_fighters

#['Bhagat Singh', 'Dadabhai Naoroji', 'Lala Lajipati Rai', 'Sarojini Naidu', 'Mahatma Gandhi', 'Mahatma Gandhi']
#['Sarojini Naidu', 'Bhagat Singh', 'Dadabhai Naoroji', 'Lala Lajipati Rai', 'Sarojini Naidu', 'Mahatma Gandhi', 'Mahatma Gandhi', 'Sarojini Naidu']
#['Sarojini Naidu', 'Bhagat Singh', 'Dadabhai Naoroji', 'Lala Lajipati Rai', 'Sarojini Naidu', 'Mahatma Gandhi', 'Mahatma Gandhi', 'Bhagat Singh', 'Sarojini Naidu']
#['Bhagat Singh', 'Dadabhai Naoroji', 'Lala Lajipati Rai', 'Sarojini Naidu', 'Mahatma Gandhi', 'Mahatma Gandhi']

print '---------------Other Functions---------------'
#sorted(freedom_fighters)
#print max(freedom_fighters)
#print min(freedom_fighters)
#print sum(list1)

Python List

List : 
A Python list contains an ordered collection of objects

E.g.,

abc = [1, 2, 3, 4, 5]

Python index of list starts from 0 (left most)
abc[0], abc[1], abc[2], abc[3], abc[4]

Python also supports negative indices from the right most, starts with -1
abc[-5], abc[-4], abc[-3], abc[-2], abc[-1]

abc[-1] is 5
abc[0] is 1



Please refer to other topics on List like :
Append to list in Python
Delete the last name from the list in Python
Remove an element from List in Python
Check an element exists in an list in Python
Python Filter Vs Map Vs List Comprehension

Please refer to Regular Expressions Concepts :
Brief on Regular Expressions
Greedy Operators in Regular Expressions in Perl
Modifiers in Regular Expressions in Perl
Capturing concept in Regular Expressions in Perl
Capture Pre Match ,Post Match, Exact match in Regular Expressions in Perl
Non Capturing Paranthesis in Regular Expressions in Perl
Substitute nth occurance in Regular Expressions in Perl
All Topics in Regular Expressions in Perl

You might also wish to read other topics like :
Python Class and Object Example
Inheritance in Python
Packages in Python
Exceptions in Python
How to remove duplicate lines from a file in Perl
How to remove duplicate lines from a file in Pyhton

Append to list in Python

inspiring_ppl = ["Mahatma Gandhi", "Mother Teresa", "Paul Coelho", "Bill Gates", "Steve Jobs"]

#raw_input(), print for Python 2.X Version 
#input(), print() for Python 3.X Version

new_insp_ppl = "prabhath"
inspiring_ppl.append(new_insp_ppl)

o/p:
inspiring_ppl = ["Mahatma Gandhi", "Mother Teresa", "Paul Coelho", "Bill Gates", "Steve Jobs", "prabhath"]



Please refer to other topics on List like :
List in Python
Append to list in Python
Delete the last name from the list in Python
Remove an element from List in Python
Check an element exists in an list in Python
Python Filter Vs Map Vs List Comprehension

Please refer to Regular Expressions Concepts :
Brief on Regular Expressions
Greedy Operators in Regular Expressions in Perl
Modifiers in Regular Expressions in Perl
Capturing concept in Regular Expressions in Perl
Capture Pre Match ,Post Match, Exact match in Regular Expressions in Perl
Non Capturing Paranthesis in Regular Expressions in Perl
Substitute nth occurance in Regular Expressions in Perl
All Topics in Regular Expressions in Perl

You might also wish to read other topics like :
Python Class and Object Example
Inheritance in Python
Packages in Python
Exceptions in Python
How to remove duplicate lines from a file in Perl
How to remove duplicate lines from a file in Pyhton

Delete the last name from the list in Python

inspiring_ppl = ["Mahatma Gandhi", "Mother Teresa", "Paul Coelho", "Bill Gates", "Steve Jobs", "Abdul Kalam"]

#raw_input(), print for Python 2.X Version 
#input(), print() for Python 3.X Version

del inspiring_ppl[-1] #removes Abdul Kalam

print ("The following inspiring_ppl are :", inspiring_ppl)
#print "The following inspiring_ppl are :", inspiring_ppl

#o/p:
#inspiring_ppl = ["Mahatma Gandhi", "Mother Teresa", "Paul Coelho", "Bill Gates", "Steve Jobs"]


Please refer to other topics on List like :
List in Python
Append to list in Python
Delete the last name from the list in Python
Remove an element from List in Python
Check an element exists in an list in Python
Python Filter Vs Map Vs List Comprehension

Please refer to Regular Expressions Concepts :
Brief on Regular Expressions
Greedy Operators in Regular Expressions in Perl
Modifiers in Regular Expressions in Perl
Capturing concept in Regular Expressions in Perl
Capture Pre Match ,Post Match, Exact match in Regular Expressions in Perl
Non Capturing Paranthesis in Regular Expressions in Perl
Substitute nth occurance in Regular Expressions in Perl
All Topics in Regular Expressions in Perl

You might also wish to read other topics like :
Python Class and Object Example
Inheritance in Python
Packages in Python
Exceptions in Python
How to remove duplicate lines from a file in Perl
How to remove duplicate lines from a file in Pyhton

Remove an element from List in Python

inspiring_ppl = ["Mahatma Gandhi", "Mother Teresa", "Paul Coelho", "Bill Gates", "Steve Jobs"]

new_inspiring_ppl = inspiring_ppl[:]

#Note:
#raw_input(), print for Python 2.X Version 
#input(), print() for Python 3.X Version

for person in new_inspiring_ppl:
     print("Do you want to keep person", person, "?")
     #print "Do you want to keep person", person, "?"
     answer = input("yes/no ")
     #answer = raw_input ("yes/no ")
     if answer != "yes":
         inspiring_ppl.remove(person)
 
print(inspiring_ppl)
#print inspiring_ppl


Please refer to other topics on List like :
List in Python
Append to list in Python
Delete the last name from the list in Python
Remove an element from List in Python
Check an element exists in an list in Python
Python Filter Vs Map Vs List Comprehension

Please refer to Regular Expressions Concepts :
Brief on Regular Expressions
Greedy Operators in Regular Expressions in Perl
Modifiers in Regular Expressions in Perl
Capturing concept in Regular Expressions in Perl
Capture Pre Match ,Post Match, Exact match in Regular Expressions in Perl
Non Capturing Paranthesis in Regular Expressions in Perl
Substitute nth occurance in Regular Expressions in Perl
All Topics in Regular Expressions in Perl

You might also wish to read other topics like :
Python Class and Object Example
Inheritance in Python
Packages in Python
Exceptions in Python
How to remove duplicate lines from a file in Perl
How to remove duplicate lines from a file in Pyhton