Python | Ways to initialize list with alphabets
While working with Python lists, sometimes we wish to initialize the list with the English alphabet a-z or A-Z. This is an essential utility in competitive programming and also in certain applications. Let’s discuss various methods to achieve this using Python.
Initialize the list with alphabets using string.ascii_uppercase
The most pythonic and latest way to perform this particular task. Using this new inbuilt function will internally handle the coding part providing a useful shorthand for the user.
Note: You can use lowercase instead of uppercase to generate lower alphabets.
Python3
import string# initializing empty listtest_list = []# using string for filling alphabetstest_list = list(string.ascii_uppercase)# printing resultant listprint ("List after insertion : " + str(test_list)) |
Output :
List after insertion : [‘A’, ‘B’, ‘C’, ‘D’, ‘E’, ‘F’, ‘G’, ‘H’, ‘I’, ‘J’, ‘K’, ‘L’, ‘M’, ‘N’, ‘O’, ‘P’, ‘Q’, ‘R’, ‘S’, ‘T’, ‘U’, ‘V’, ‘W’, ‘X’, ‘Y’, ‘Z’]
Initialize the list with alphabets using a naive method
The most general method that comes to our mind is using the brute force method of running a Python loop till 26 and incrementing it while appending the letters in the list. Refer to ASCII Table for more.
Python3
# initializing empty listtest_list = []# printing initial listprint ("Initial list : " + str(test_list))# using naive method# for filling alphabetsalpha = 'a'for i in range(0, 26): test_list.append(alpha) alpha = chr(ord(alpha) + 1)# printing resultant listprint ("List after insertion : " + str(test_list)) |
Output :
Initial list : []
List after insertion : [‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’, ‘g’, ‘h’, ‘i’, ‘j’, ‘k’, ‘l’, ‘m’, ‘n’, ‘o’, ‘p’, ‘q’, ‘r’, ‘s’, ‘t’, ‘u’, ‘v’, ‘w’, ‘x’, ‘y’, ‘z’]
Initialize the list with alphabets using list comprehension
This is a method similar to the above method, but rather a shorthand for the naive method as it uses the list comprehension technique to achieve the task.
Python3
# Python3 code to demonstrate# Filling alphabets# using list comprehension# initializing empty listtest_list = []# printing initial listprint ("Initial list : " + str(test_list))# using list comprehension# for filling alphabetstest_list = [chr(x) for x in range(ord('a'), ord('z') + 1)]# printing resultant listprint ("List after insertion : " + str(test_list)) |
Output :
Initial list : []
List after insertion : [‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’, ‘g’, ‘h’, ‘i’, ‘j’, ‘k’, ‘l’, ‘m’, ‘n’, ‘o’, ‘p’, ‘q’, ‘r’, ‘s’, ‘t’, ‘u’, ‘v’, ‘w’, ‘x’, ‘y’, ‘z’]
Initialize the list with alphabets using a map()
Using a map() is an elegant way to perform this particular task. It type casts the numbers in a range to a particular data type, char in this case, and assigns them to the list.
Python3
# initializing empty listtest_list = []# printing initial listprint ("Initial list : " + str(test_list))# using map()# for filling alphabetstest_list = list(map(chr, range(97, 123)))# printing resultant listprint ("List after insertion : " + str(test_list)) |
Output :
Initial list : []
List after insertion : [‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’, ‘g’, ‘h’, ‘i’, ‘j’, ‘k’, ‘l’, ‘m’, ‘n’, ‘o’, ‘p’, ‘q’, ‘r’, ‘s’, ‘t’, ‘u’, ‘v’, ‘w’, ‘x’, ‘y’, ‘z’]
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