Lists

Lists are constructed with square brackets with elements separated by a comma.

Lists are mutable, meaning the individual items in the list can be changed.

Example 1



In [1]:

    
vowels = ['a','e','i','o','u']
print(vowels)









    



['a', 'e', 'i', 'o', 'u']

Example 2

Lists can also hold multiple object types



In [2]:

    
list1 = [1,'a',"This is a list",5.25]
print(list1)









    



[1, 'a', 'This is a list', 5.25]

Example 3



In [3]:

    
# Find the length of the list
len(list1)









    Out[3]:





4

Example 4 - Slicing & Indexing



In [4]:

    
# Get the element using the index
print(list1[0])
print(list1[2])









    



1
This is a list



In [17]:

    
# Grab index 1 and everything after it
print(list1[1:])









    



['a', 'This is a list', 5.25]



In [18]:

    
# Grab the element from index position 1 to 3 (1 less than given)
print(list1[1:3])









    



['a', 'This is a list']



In [20]:

    
# Grab elements upto 3rd item
print(list1[:3])









    



[1, 'a', 'This is a list']



In [10]:

    
# Grab the last item in the list
print(list1[-1])



In [25]:

    
print(list1[-1:])









    



[5.25]



In [26]:

    
# Third parameter is the jump parameter
list2 = ['a','b','c','d','e','f','g']
list2[1:4:2]









    Out[26]:





['b', 'd']



In [27]:

    
# Concatenate Elements
list2 + ["added"]









    Out[27]:





['a', 'b', 'c', 'd', 'e', 'f', 'g', 'added']



In [28]:

    
# unless reassigned the added item is not permanently added
list2









    Out[28]:





['a', 'b', 'c', 'd', 'e', 'f', 'g']



In [29]:

    
list2 = list2 + ["added permanently"]
list2









    Out[29]:





['a', 'b', 'c', 'd', 'e', 'f', 'g', 'added permanently']



In [30]:

    
list3 = list2 * 2
list3









    Out[30]:





['a',
 'b',
 'c',
 'd',
 'e',
 'f',
 'g',
 'added permanently',
 'a',
 'b',
 'c',
 'd',
 'e',
 'f',
 'g',
 'added permanently']

List Methods



In [31]:

    
list4 = ['a','b','d','e']
list4.insert(2,'c')
list4









    Out[31]:





['a', 'b', 'c', 'd', 'e']



In [33]:

    
list4.append(['f','g'])
list4









    Out[33]:





['a', 'b', 'c', 'd', 'e', ['f', 'g']]



In [34]:

    
popped_item = list4.pop()
popped_item









    Out[34]:





['f', 'g']



In [35]:

    
print(list4)









    



['a', 'b', 'c', 'd', 'e']



In [36]:

    
# sort elements
list4.sort()
list4









    Out[36]:





['a', 'b', 'c', 'd', 'e']



In [37]:

    
# reverse elements
list4.reverse()
list4









    Out[37]:





['e', 'd', 'c', 'b', 'a']



In [38]:

    
list4.remove('a')
list4









    Out[38]:





['e', 'd', 'c', 'b']



In [39]:

    
list5 = ['a','f']
list4.extend(list5)
list4









    Out[39]:





['e', 'd', 'c', 'b', 'a', 'f']



In [40]:

    
del list4[2]
list4









    Out[40]:





['e', 'd', 'b', 'a', 'f']



In [42]:

    
# count the items
list4.count('a')









    Out[42]:





1



In [45]:

    
# check if item exists in a list
if 'a' in list4:
    print('found')









    



found



In [46]:

    
print(list4.index('a'))