#PYTHON(DAY7)List methods in python

                                             #PYTHON(DAY7)

Methods in Python

Python List Methods has multiple methods to work with Python lists

We use dir() function to print the built-in list methods

print(dir(list))

And the expected output is:
['__add__', '__class__', '__class_getitem__', '__contains__', '__delattr__', '_delitem__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', '__init_subclass__', '__iter__', '__le__', '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', 'append', 'clear', 'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort'['__add__', '__class__', '__class_getitem__', '__contains__', '__delattr__', '__delitem__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', '__init_subclass__', '__iter__', '__le__', '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', 'append', 'clear', 'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']

append()

• append is used to add another element to the list and this element will be added at the end

x = [1,2,3,4]
print(x, id(x))
print()
x.append(5)
print(x,id(x))

Note: we can not append 2 elements into the list at a time

so, from the above code we get the error as list.append() takes exactly one value

extend()

• extend is used to add two or more than two elements to end of the list
• these values/elements should be passed in container

x = [1,2,3,4]
print(x)
x.extend([5,6])
print(x)

And the expected output for the above code is: [1,2,3,4,[5,6]]

count()

• count will return the frequency of given element

x = [1,2,3,4,6]
print(x)
print(x.count(1))
print(x.count(5))

And the expected output is:

[1,2,3,4,6]
1
0

insert()

• insert as name suggests, is going to insert a new element at the specified index position
• index takes two values i.e index and value

x = [1,2,4]
print(x)
x.insert(3,1)
print(x)

And the expected output is:

[1,2,4,3]

remove()

• remove() is used to remove the specified element
• it removes the first occurence

x = [4,1,2,3,4,4]
x.remove(4)
print(x)

And the expected output is: here the first occurence is removed

[1,2,3,4,4]

pop()

• pop removes the element at given index position, if no index value is passed, the last element will popped out
• the discard/ejected element can be captured/assigned to a new for further use

x = [1,2,3,4,5]
x.pop(3)
print(x)

And the expected output is:

[1,2,3,5]

Note: as the element is popped out, the index values changes

so, from the below code we get the error as pop index out of range

x = [1,2,3,5]
x.pop(4)
print(x)

However, the remove() works on the elements and pop() works on indexes of elements

reverse()

• it reverses the list

x = [1,2,3]
print(x)
x.reverse()
print(x)

And the expected output is:

[1,2,3]
[3,2,1]

sort()

• sorting in ascending or descending

a = list(range(1,11))
b = [4.5,3.8,44.23,2,8,-6.9]
print(a,b, sep = '\n')

And the expected output is:

[1,2,3,4,5,6,7,8,9,10]
[4.5,3.8,44.23,2,8,-6.9]

print(a)
a.sort()
print(a) # ascending
a.sort(reverse = True) # decending
print(a)

And the expected output is:

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
[10, 9, 8, 7, 6, 5, 4, 3, 2, 1]

copy()

• copy is used to store the list in different location to stor it in the different location

e = [1,2,3]
f = e
print(e,f,sep = '\n')
print(id(e), id(f))

e.insert(0,11)
print(e, f, sep ='\n')
print(id(e), id(f))

[1, 2, 3]
[1, 2, 3]
2590467336704 2590467336704
[11, 1, 2, 3]
[11, 1, 2, 3]
2590467336704 2590467336704

clear()

• it is going to erase all the elements from the list and returns an empty list

f = [1,2,3,4]
f.clear()
print(f)

And the expected output is: [ ] (empty list)