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MLOps engineer at Deloitte.
MLOps engineer at Deloitte.
There are many advantages to using lists in Python. Although lists are similar to arrays in other languages, the main difference between lists and arrays is that lists dont need to have the same data type. Another major advantage is that lists are mutable, which means we can change a list even after we create it.
Creating Lists in Python
First, lets talk about how to create a list. In Python, we create lists using square brackets. We separate each item in the list with a comma.
my_list = [I,think,Built In,is,number,1] type[my_list] Output: listYou can see Ive added both string and numeric data types inside the same list.
Indexing Lists
Lists in Python are indexed and have a defined count. The elements in a list are likewise indexed according to a defined sequence with 0 being the first item and n-1 being the last [n is the number of items in a list]. Each item in the list has its indexed place.
Our list index starts with 0 and ends with 5, which we can check using the pre-built len[] function:
len[my_list] Output: 6We can also check each item value based on its index:
my_list[0],my_list[3] Output: [I, is]Read more about Python 5 Dunder Methods in Python You Should Know
Append Method
The append[] method in Python adds a single item to the end of the existing list.
After appending to the list, the size of the list increases by one.
Syntax
list_name.append[item]
Parameters
The append[] method takes a single item as an input parameter and adds that to the end of the list.
Items you can Append in a Python List
- Numbers
- Strings
- Boolean data types
- Dictionaries
- Lists
Adding Numbers to a List
Lets look at how to add a new numeric item to a list:
# list of strings string_list = [Built In,Python,Machine Learning,Data Science] #adding a new int item to the string_list string_list.append[1] #printing appended list print[string_list] Output: [Built In,Python,Machine Learning,Data Science,1]Adding a List to a List
In addition to adding a strings or numeric data types, we can also append separate lists to a list:
You can see from the output that a new list is appended at the end of our old list.
To get the whole list as an indexed item, well use:
string_list[5] Output: [1,2,3,4,5]If you want to access the elements from this list you can do that in the same way as you access elements from a 2-D matrix.
string_list[5][1] Output: 2If you try to access an item with an index greater than the list index youll get an index error.
string_list[6] Output: - IndexError Traceback [most recent call last] in 1 string_list[6] IndexError: list index out of rangeWith these code samples, we can append different data types to a list and access them with ease. This is just one of the many methods we can use in Python lists that make life easier for any Python developer.
This post was originally published on Towards Data Science.