5 Best Ways to Remove the Nth Index Character from a Non-Empty String in Python

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💡 Problem Formulation: In Python, one might often need to remove a character at a specific index from a string. This task involves accepting a non-empty string as input, and producing an output where the character at the nth index has been removed. For instance, if the input is "Python" and the nth index is 1, the expected output would be "Pthon".

Method 1: String Concatenation

String concatenation in Python can be used to exclude the nth character from a string. This approach takes the substring before the nth index and concatenates it with the substring starting from one character after the nth index.

Here’s an example:

def remove_nth_char(original, n):
    return original[:n] + original[n+1:]

print(remove_nth_char("Python", 1))

Output: Pthon

This function, remove_nth_char, excludes the character at the specified index (n) by slicing the string and joining the pieces without the nth character. String slicing in Python is efficient and is a common practice for string manipulation.

Method 2: Using the str.replace() Method with a Count Limit

The str.replace() method in Python can replace occurrences of a substring within a string with another substring. By setting a count limit, it is possible to target the nth occurrence specifically for replacement.

Here’s an example:

def remove_nth_char(original, n):
    target = original[n]
    # Replace first occurrence of target from the nth position
    return original[:n] + original[n:].replace(target, '', 1)

print(remove_nth_char("Balloon", 2))

Output: Baloon

This code carefully replaces the nth character by using str.replace with a count of 1, ensuring only the targeted character is removed. However, this method has a limitation that it may not work correctly if the nth character has multiple occurrences starting from that index.

Method 3: Using List Mutability

This method leverages the fact that lists in Python are mutable, meaning we can change their contents. Strings are immutable; however, we can convert them to a list of characters, remove the nth character, and then join the list back into a string.

Here’s an example:

def remove_nth_char(original, n):
    chars = list(original)
    del chars[n]
    return ''.join(chars)

print(remove_nth_char("Documentation", 5))

Output: Documntation

The function converts the string to a list, deletes the nth character, and then joins the list back into a string. This method is particularly useful when multiple mutations are to be performed on the string.

Method 4: Using a Generator Expression

A generator expression in Python is a concise way to process each item in an iterable and generate results on-the-fly. You can use a generator expression to include all characters except the one at the nth index, and then join everything into a new string.

Here’s an example:

def remove_nth_char(original, n):
    return ''.join(char for index, char in enumerate(original) if index != n)

print(remove_nth_char("Ingenious", 4))

Output: Ingeious

The function iterates over the string with an index and filters out the character at the nth index using a generator expression. This is efficient for larger strings as it doesn’t create an intermediate list.

Bonus One-Liner Method 5: Using a Lambda Function

A one-liner technique to remove the nth character from a string involves using a lambda function within a map function. This method leverages the fact that map can apply a function to each item of an iterable.

Here’s an example:

remove_nth_char = lambda s, n: ''.join(map(lambda x: x[1], filter(lambda x: x[0] != n, enumerate(s))))

print(remove_nth_char("Exceptional", 3))

Output: Exceitional

The lambda function provided to map returns only the characters whose index is not n, effectively skipping the nth character. Although concise, this one-liner may not be as readable as the other methods.

Summary/Discussion

  • Method 1: String Concatenation. Efficient for small strings. Easy to read and understand.
  • Method 2: str.replace() with Count. Can target specific occurrences. Limited when multiple identical characters exist in succession.
  • Method 3: Using List Mutability. Excellent for multiple string mutations. Requires converting between a string and a list.
  • Method 4: Using a Generator Expression. Suitable for larger strings. Generator incurs less memory overhead.
  • Method 5: Lambda One-Liner. Very concise. Potentially difficult to read and understand for those unfamiliar with lambda and map functions.