Remove character in a String except Alphabet

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

Example

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

Program to Remove characters in a string except alphabets

Below are the steps and methods by which we can remove all characters other than alphabets using List Comprehension and ord() in Python:

• Using ord() and range()
• Using filter() and lambda
• Using isalpha()

Remove All Characters Other Than Alphabets using ord() and range()

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 that ranges from an inclusive to b exclusive with increment/decrement of a given step. In this example, we are using ord() and range() to remove all characters other than alphabets.

Python3

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

Python Remove All Characters Using filter() and lamda

In this example, we are using filter() and lambda to remove all characters other than alphabets.

Python3

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

Output

GeeksforGeeks

Remove Characters Other Than Alphabets Using isalpha()

In this example, we are using isalpha(). Here, we are converting 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.

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))

Output

GeeksforGeeks

Time complexity: O(n), where n is length of string
Auxiliary Space: O(n)