Python Program to Find Indices of the Non-Zero Elements in the Python list

We’ll look at how to determine the indices of non-zero entries in a Python list. There may be times when we simply need to access the list’s non-zero elements. In such instances, we can apply the following techniques.

Lists:

A list is an ordered grouping of values. It can hold a variety of values. A list is a container that may be changed. This means that we can add new values, delete old ones, or change current ones.

A Python list is a mathematical concept that describes a finite sequence. Items or elements in a list are the values in a list. A list can have multiple instances of the same value. Each occurrence is treated as a separate item.

Given a list, the task is to find the indices of non-zero elements in the given list.

Examples:

Example1:

Input:

Given list = [11, 19, 0, 8, 45, 0, 29, 0, 19, 0, 26, 0, 33]

Output:

The non zero elements indices in the given list are =  [0, 1, 3, 4, 6, 8, 10, 12]

Example2:

Input:

Given list = 25 0 7 0 0 0 9 5

Output:

The non zero elements indices in the given list are = [0, 2, 6, 7]

Program to Find Indices of the Non-Zero Elements in the Python list in Python

Below are the ways to find the indices of non-zero elements in the given list.

Using For loop(Static Input)
Using For loop(User Input)
Using List Comprehension (Static Input)
Using List Comprehension (User Input)

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Method #1: Using For Loop (Static Input)

Approach:

Give the list as static input and store it in a variable.
Take an empty list and initialize it’s with an empty list using list() and [].
Calculate the length of the given list using the len() function.
Loop till the length of the given list using the For loop.
Check if the element in the given list is equal to 0 or not using the If conditional statement.
If it is a non-zero element then append the index to the new list using the append() function.
Print the index list.
The Exit of the Program.

Below is the implementation:

# Give the list as static input and store it in a variable.
gvnlst = [11, 19, 0, 8, 45, 0, 29, 0, 19, 0, 26, 0, 33]
# Take an empty list and initialize it’s with an empty list using list() and [].
nwlist = []
# Calculate the length of the given list using the len() function.
gvnlstlen = len(gvnlst)
# Loop till the length of the given list using the For loop.
for m in range(gvnlstlen):
    # Check if the element in the given list is equal to 0 or not
    # using the If conditional statement.
    if(gvnlst[m] != 0):
        # If it is non-zero element then append the index to the new list
        # using the append() function.
        nwlist.append(m)
# Print the index list.
print('The non zero elements indices in the given list are = ', nwlist)

Output:

The non zero elements indices in the given list are =  [0, 1, 3, 4, 6, 8, 10, 12]

Method #2: Using For Loop (User Input)

Approach:

Give the number as user input using the int(input()) function and store it in a variable.
Take an empty list and initialize it’s with an empty list using list() and [].
Calculate the length of the given list using the len() function.
Loop till the length of the given list using the For loop.
Check if the element in the given list is equal to 0 or not using the If conditional statement.
If it is a non-zero element then append the index to the new list using the append() function.
Print the index list.
The Exit of the Program.

Below is the implementation:

# Give the list as user input using list(),map(),input(),and split() functions.
# Store it in a variable.
gvnlst = list(map(int, input(
    'Enter some random List Elements separated by spaces = ').split()))
# Take an empty list and initialize it’s with an empty list using list() and [].
nwlist = []
# Calculate the length of the given list using the len() function.
gvnlstlen = len(gvnlst)
# Loop till the length of the given list using the For loop.
for m in range(gvnlstlen):
    # Check if the element in the given list is equal to 0 or not
    # using the If conditional statement.
    if(gvnlst[m] != 0):
        # If it is non-zero element then append the index to the new list
        # using the append() function.
        nwlist.append(m)
# Print the index list.
print('The non zero elements indices in the given list are = ', nwlist)

Output:

Enter some random List Elements separated by spaces = 25 0 7 0 0 0 9 5
The non zero elements indices in the given list are = [0, 2, 6, 7]

Method #3: Using List Comprehension (Static Input)

The method used in the sample program is another way to find the indices of non-zero elements. This is a concise summary implementation of the preceding algorithm. To transform the list into an iterable, we use the enumerate() method in this method.

Approach:

Give the list as static input and store it in a variable.
Use the list comprehension and enumerate to find all non-zero elements indices in the given list.
Print this indices list.
The Exit of the Program.

Below is the implementation:

# Give the list as static input and store it in a variable.
gvnlst = [11, 19, 0, 8, 45, 0, 29, 0, 19, 0, 26, 0, 33]
# Use the list comprehension and enumerate to find all non-zero elements
# indices in the given list.
nwlist = [index for index, listelement in enumerate(
    gvnlst) if listelement != 0]
# Print the index list.
print('The non zero elements indices in the given list are = ', nwlist)

Output:

The non zero elements indices in the given list are =  [0, 1, 3, 4, 6, 8, 10, 12]

Method #4: Using List Comprehension (User Input)

Approach:

Give the number as user input using the int(input()) function and store it in a variable.
Use the list comprehension and enumerate to find all non-zero elements indices in the given list.
Print this indices list.
The Exit of the Program.

Below is the implementation:

# Give the list as user input using list(),map(),input(),and split() functions.
# Store it in a variable.
gvnlst = list(map(int, input(
    'Enter some random List Elements separated by spaces = ').split()))
# Use the list comprehension and enumerate to find all non-zero elements
# indices in the given list.
nwlist = [index for index, listelement in enumerate(
    gvnlst) if listelement != 0]
# Print the index list.
print('The non zero elements indices in the given list are = ', nwlist)

Output:

Enter some random List Elements separated by spaces = 7 9 0 0 6 3 0 0
The non zero elements indices in the given list are = [0, 1, 4, 5]

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