List operations in python – Ways to insert elements

Lists are one of the best data structures I have ever seen. Storing and extracting values from it is a breeze (most of the time).
Python has a huge number of concepts and functions that work on the lists to maintain, update and extract  data.
List splicing, sorting , appending , searching , inserting and removing data are some of the operations that can be performed.

Among all these, I found two methods similar. The append() and the  extend() . What these basically do is put elements at the end of a list.But they do have a striking difference.
for example consider a list:

list_sample =  [1, 'name', 2, 3, 'True']


What the append() does is, puts whatever item which is specified,into the list along with the item’s data structure.
SO on the list_sample if we append another list ,say [‘a’ , ‘b’ ,’c’] we get:

list_sample.append( ['a' , 'b' ,'c'])
list_sample
>>>[1, 'name' , 2, 3, 'True', ['a' , 'b', 'c']]

 The append()  here, has stored the entire list in sample_list as a single list item.

On the other hand, lets use extend() on list_sampleWe shall  extend the list_sample with another list [‘d’, ‘e’, ‘f’].

list_sample.extend(['d', 'e', 'f'])
list_sample
[1, 'name', 2, 3, 'True', 'd', 'e', 'f']

here extend() has extracted each value from the list ([‘d’, ‘e’, ‘f’] ) and inserted them individually at the end of sample_list.

Other ways to add elements in a list is by using the  + (plus) operator. for example on the same defined list ,list_sample , we shall add 3 elements [‘False’, 9 , ‘h’]

list_sample = list_sample + ['False', 9 , 'h']
list_sample
>>>[1, 'name', 2, 3, 'True', 'False', 9 , 'h']

Elements can be added into the list at a particular position by making use of the insert() function. It takes in 2 arguments as  inputs, the first specifies the position to be inserted in  and second specifies the element to be inserted.

list_sample
>>>[1, 'name', 2, 3, 'True']
list_sample.insert(3,'value')
>>>[1, 'name', 2, 3, 'value',  'True'] 

So the string, ‘value’ is inserted at the position 4 (index 3) in  sample_list.

These were some of the ways in which elements can be added into a list. Different methods are used in different situations to add the elements efficiently  and quickly. That is, a single method is not relied upon to get the job done always.

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akshay pai

I am a data science engineer and I love working on machine learning problems. I have experience in computer vision, OCR and NLP. I love writing and sharing my knowledge with others. This is why I created Source Dexter. Here I write about Python, Machine Learning, and Raspberry Pi the most. I also write about technology in general, books and topics related to science. I am also a freelance writer with over 3 years of writing high-quality, SEO optimized content for the web. I have written for startups, websites, and universities all across the globe. Get in Touch! We can discuss more.

One thought on “List operations in python – Ways to insert elements

  • September 10, 2013 at 3:23 am
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    “+” operator is not so cool,try iterator and yield. the “+” is not efficient.I know it is easy to read.Hope that helps.

    Reply

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