List comprehension and ord() in Python to remove all characters other than alphabets

Given a string consisting of alphabets and other characters, remove all the characters other than alphabets and print the string so formed. Examples:

Input : str = "$Gee*k;s..fo, r'Ge^eks?"
Output : GeeksforGeeks

This problem has existing solution please refer Remove all characters other than alphabets from string link. We will solve this problem in python quickly using List Comprehension.

Approach : is

1. Traverse string 
2. Select characters which lie in range of [a-z] or [A-Z]
3. Print them together

How does ord() and range() function works in python ?

The ord() method returns an integer representing the Unicode code point of the given Unicode character.For example,

 ord('5') = 53 and ord('A') = 65 and ord('$') = 36

The range(a,b,step) function generates a list of elements which ranges from a inclusive to b exclusive with increment/decrement of given step.

Python3

# Python code to remove all characters
# other than alphabets from string
 
def removeAll(input):
 
    # Traverse complete string and separate
    # all characters which lies between [a-z] or [A-Z]
    sepChars = [char for char in input if
ord(char) in range(ord('a'),ord('z')+1,1) or ord(char) in
range(ord('A'),ord('Z')+1,1)]
 
    # join all separated characters
    # and print them together
    return ''.join(sepChars)
 
# Driver program
if __name__ == "__main__":
    input = "$Gee*k;s..fo, r'Ge^eks?"
    print (removeAll(input))

Output:

GeeksforGeeks

Python3

# code
string = "$Gee*k;s..fo, r'Ge^eks?"
print("".join(filter(lambda x : x.isalpha(),string)))

Approach#3: Using isalpha()

Convert the input string into a list of characters. Loop through the list of characters. If the current character is not an alphabet, replace it with an empty string. Join the list of characters back into a string. Return the resulting string.

Algorithm

1. Define a function called remove_non_alpha_chars that takes a string as input.
2. Convert the input string into a list of characters.
3. Loop through the list of characters.
4. If the current character is not an alphabet, replace it with an empty string.
5. Join the list of characters back into a string.
6. Return the resulting string.

Python3

def remove_non_alpha_chars(s):
    chars = list(s)
    for i in range(len(chars)):
        if not chars[i].isalpha():
            chars[i] = ''
    return ''.join(chars)
s="$Gee*k;s..fo, r'Ge^eks?"
print(remove_non_alpha_chars(s))