Lists
by shashank21jWhen we talk about storing multiple values in a container-like data structure, the first thing that comes to mind is a list.
You can initialize a list as:
arr = list()
# or simply
arr = []
or with a few elements as:
arr = [1,2,3]
Elements can be accessed easily similar to most programming languages:
print arr[0]
# result is 1
print arr[0] + arr[1] + arr[2]
# result is 6
Lists in Python are very versatile. You can add almost anything in a Python list.
In Python, you can create a list of any objects: strings, integers, or even lists. You can even add multiple types in a single list!
Let's look at some of the methods you can use on list.
1.) append(x)
Adds a single element x to the end of a list.
arr.append(9)
print arr
# prints [1, 2, 3, 9]
2.) extend(L)
Merges another list L to the end.
arr.extend([10,11])
print arr
# prints [1, 2, 3, 9, 10, 11]
3.) insert(i,x)
Inserts element x at position i.
arr.insert(3,7)
print arr
# prints [1, 2, 3, 7, 9, 10, 11]
4.) remove(x)
Removes the first occurrence of element x.
arr.remove(10)
arr
# prints [1, 2, 3, 7, 9, 11]
5.) pop()
Removes the last element of a list. If an argument is passed, that index item is popped out.
temp = arr.pop()
print temp
# prints 11
6.) index(x)
Returns the first index of a value in the list. Throws an error if it's not found.
temp = arr.index(3)
print temp
# prints 2
7.) count(x)
Counts the number of occurrences of an element x.
temp = arr.count(1)
print temp
# prints 1
8.) sort()
Sorts the list.
arr.sort()
print arr
# [1, 2, 3, 7, 9]
9.) reverse()
Reverses the list.
arr.reverse()
print arr
# [9, 7, 3, 2, 1]