\\nHow to print out the first character of each list in Python?

A Python list is a built-in, mutable datatype that stores multiple items or elements, separated by commas, within square brackets [ ]. The index of a list in Python starts from 0 up to length-1. We can retrieve/access elements at a particular index as follows -

list_name[index] 

The given task is to write a Python program that prints the first character of each element in a list. But, before that, let's see some example scenarios:

Scenario 1

For example, if our list contains string values, the output should be the first character of each string.

Input: list = ['aaa','bbb','ccc']
Output: new_list = [a, b, c]
Explanation:
Look at the input list, it has 3 strings. 
The first string starts with character 'a' 
The second one with 'b' 
The third one with 'c'. Hence, the output is [a, b, c].  

Scenario 2

Similarly, if our list contains (sub) lists, the output should be the first element of each sublist.

Input: list = [[12, 123, 1234], [9, 98, 987], [56, 456, 3475]]
Output: new_list = [12, 9, 56]
Explanation:
The input list has 3 sublists. 
The first element of 1st sublist is '12'
The first element of 2nd sublist is '9' 
The first element of the 3rd sublist is '56'. Therefore, the result would be [12, 9, 56]

Printing the First Character of Each List in Python

In Python, we can print the first character of each element in a list in the following ways:

• Using a for loop
• Using list comprehension
• Using map() and a lambda function

Using a for Loop

In Python, using the for loop, we can iterate through each element in any iterable object. To print or retrieve the first characters of each element in a list, we need to iterate through its elements.

At each iteration, we need to append the character at index 0 (of the element) to a new, empty list.

Example: 1

In the following Python program, we are defining a list of lists, and then using a for loop, we are printing the first element of each sublist -

L1=[[1,1,1],[2,2,2],[3,3,3]]
print("First Character of each list: ")
first_chars = []
for i in range(len(L1)):
    first_chars.append(L1[i][0])
print(first_chars)

Output of the above code is:

First Character of each list: 
[1, 2, 3]

Example: 2

In this example, let us define a list with string values, and obtain the first character of each string using the for loop -

L1 = ['aaa','bbb','ccc']
print("First Character of each string: ")
for string in L1:
   print (string[0])

Following is the output of the above code -

First Character of each string: 
a
b
c

Using List Comprehension

The list comprehension in Python helps us to create a list by performing an operation on each element of an iterable. The result of the operation is returned as a new list.

To retrieve the first character of each element, we need to use ele[0] as an operation on the desired list.

Example:

In the following example, we are printing the first element of each element of a list of lists using a list comprehension -

L1=[[1,2,3],[4,5,6],[7,8,9]]
print("First Character of each list: ")
first_chars = [ele[0] for ele in L1]
print(first_chars)

On running this code, it will print the following result -

First Character of each list: 
[1, 4, 7]

Using map() Function

The Python map() function accepts a function and an iterable as parameters, applies the specified function to each item in the given iterable.

To find the first character from each element in a list, we pass the lambda function to map(), which will find the first element and store it in another list.

Example:

In the following example, we are printing the first element of each sublist (of a list) using the map() function -

L1=[[1,1,1],[2,2,2],[3,3,3]] 
print("First Character of each list: ")
first_chars = list(map(lambda s: s[0], L1))
print(first_chars) 

On executing the above code will print the first character from the list as shown below:

First Character of each list: 
[1, 2, 3]

Conclusion

In this article, we learned how to find the first character of each element in a given Python list. To solve this problem, we traversed the list using a for loop, list comprehension, and the map() function with a lambda expression, and displayed the character at index 0.