Python | Add tuple to front of list

Sometimes, while working with Python list, we can have a problem in which we need to add a new tuple to existing list. Append at rear is usually easier than addition at front. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using insert()

This is one of the way in which the element can be added to front in one-liner. It is used to add any element in front of list. The behaviour is the same for tuple as well. 

Python3

# Python3 code to demonstrate working of
# Adding tuple to front of list
# using insert()

# Initializing list
test_list = [('is', 2), ('best', 3)]

# printing original list
print("The original list is : "
      + str(test_list))

# Initializing tuple to add
add_tuple = ('gfg', 1)

# Adding tuple to front of list
# using insert()
test_list.insert(0, add_tuple)

# printing result
print("The tuple after adding is : "
      + str(test_list))

Output

The original list is : [('is', 2), ('best', 3)]
The tuple after adding is : [('gfg', 1), ('is', 2), ('best', 3)]

Time complexity: O(n) where n is the number of elements in the list as we are inserting an element in the front of the list which takes linear time.
Auxiliary Space: O(1) as we are not using any extra data structure and only inserting an element in the existing list.

Method #2 : Using deque() + appendleft()

The combination of above functions can be used to perform this particular task. In this, we just need to convert the list into a deque so that we can perform the append at front using appendleft() 

Python3

# Python3 code to demonstrate working of
# Adding tuple to front of list
# using deque() + appendleft()
from collections import deque

# Initializing list
test_list = [('is', 2), ('best', 3)]

# printing original list
print("The original list is : " + str(test_list))

# Initializing tuple to add
add_tuple = ('gfg', 1)

# Adding tuple to front of list
# using deque() + appendleft()
res = deque(test_list)
res.appendleft(add_tuple)

# printing result
print("The tuple after adding is : " + str(list(res)))

Output

The original list is : [('is', 2), ('best', 3)]
The tuple after adding is : [('gfg', 1), ('is', 2), ('best', 3)]

Time complexity: O(1), where n is the length of the list.
Auxiliary space: O(1)

Method #3 : Using extend() method

Python3

# Python3 code to demonstrate working of
# Adding tuple to front of list

# Initializing list
test_list = [('is', 2), ('best', 3)]

# printing original list
print("The original list is : " + str(test_list))

# Initializing tuple to add
add_tuple = ('gfg', 1)

# Adding tuple to front of list
x = [add_tuple]
x.extend(test_list)
# printing result
print("The tuple after adding is : " + str(x))

Output

The original list is : [('is', 2), ('best', 3)]
The tuple after adding is : [('gfg', 1), ('is', 2), ('best', 3)]

Time Complexity: O(k), Where k is the length of the list that needs to be added.
Auxiliary Space: O(k)

Method #4: Using the concatenation operator
You can use the + operator to concatenate the list and the tuple, and it will add the tuple to the front of the list.

Python3

# Python3 code to demonstrate working of
# Adding tuple to front of list
# using concatenation operator
# Initializing list
test_list = [('is', 2), ('best', 3)]

# printing original list
print("The original list is : " + str(test_list))

# Initializing tuple to add
add_tuple = ('gfg', 1)

# Adding tuple to front of list
test_list = [add_tuple] + test_list

# printing result
print("The tuple after adding is : " + str(test_list))
# This code is contributed by Edula Vinay Kumar Reddy

Output

The original list is : [('is', 2), ('best', 3)]
The tuple after adding is : [('gfg', 1), ('is', 2), ('best', 3)]

Time Complexity: O(k), Where k is the length of the list that needs to be added.
Auxiliary Space: O(k)

Method #5 : Using slicing and unpacking

This method creates a new list that consists of the new tuple followed by the existing list, using the * operator to unpack the elements of the existing list.

Python3

# Python3 code to demonstrate working of
# Adding tuple to front of list
# using slicing and unpacking
# Initializing list
test_list = [('is', 2), ('best', 3)]

# printing original list
print("The original list is : " + str(test_list))

# Initializing tuple to add
add_tuple = ('gfg', 1)

# Adding tuple to front of list
test_list = [add_tuple, *test_list]

# printing result
print("The tuple after adding is : " + str(test_list))

# This code is contributed by Edula Vinay Kumar Reddy

Output

The original list is : [('is', 2), ('best', 3)]
The tuple after adding is : [('gfg', 1), ('is', 2), ('best', 3)]

Time complexity: O(n), where n is the length of the list, because creating a new list using slicing and unpacking requires iterating over all the elements of the existing list.
Auxiliary space: O(n+1), because it creates a new list that is one element longer than the original list. The additional element is the new tuple that is being added to the front of the list.

Method 6: Using list comprehension and the append() method

1. Initialize the list test_list and print it.
2. Initialize the tuple add_tuple and print it.
3. Use a list comprehension to create a new list with the add_tuple at the beginning and the rest of the elements from test_list.
4. Use the append() method to add each element from the new list to test_list.
5. Print the updated list.

Python3

# Initializing list
test_list = [('is', 2), ('best', 3)]

# printing original list
print("The original list is : " + str(test_list))

# Initializing tuple to add
add_tuple = ('gfg', 1)

# Adding tuple to front of list
test_list = [add_tuple] + [i for i in test_list]

# Printing result
print("The tuple after adding is : " + str(test_list))

# Alternative method
test_list = [('is', 2), ('best', 3)]

# printing original list
print("The original list is : " + str(test_list))

# Initializing tuple to add
add_tuple = ('gfg', 1)

# Adding tuple to front of list
new_list = [add_tuple] + [i for i in test_list]

# Using append() method to add elements from new_list to test_list
for i in new_list:
    test_list.append(i)

# Printing result
print("The tuple after adding is : " + str(test_list))

Output

The original list is : [('is', 2), ('best', 3)]
The tuple after adding is : [('gfg', 1), ('is', 2), ('best', 3)]
The original list is : [('is', 2), ('best', 3)]
The tuple after adding is : [('is', 2), ('best', 3), ('gfg', 1), ('is', 2), ('best', 3)]

Time complexity: O(n) for both methods as we need to create a new list and append elements to the existing list.
Auxiliary space: O(n) for the first method and O(2n) for the second method.

Method #7 : Using the unpacking operator (*) and the list() constructor

1. Initialize the list “test_list” with the tuples
2. Initialize the tuple “add_tuple” with the tuple to add to the front of the list
3. Create a new list using the unpacking operator (*) to unpack the “add_tuple” and the original list “test_list”
4. Use the list() constructor to create a new list from the unpacked elements
5. Print the modified list.

Python3

# Initializing list
test_list = [('is', 2), ('best', 3)]

# Printing original list
print("The original list is : " + str(test_list))

# Initializing tuple to add
add_tuple = ('gfg', 1)

# Adding tuple to front of list
new_list = [add_tuple, *test_list]
test_list = list(new_list)

# Printing result
print("The tuple after adding is : " + str(test_list))

Output

The original list is : [('is', 2), ('best', 3)]
The tuple after adding is : [('gfg', 1), ('is', 2), ('best', 3)]

Time complexity: O(n) (where n is the length of the list)
Auxiliary space: O(n)