Python Program to Create a String from the First and Last 2 Characters of a Given String

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๐Ÿ’ก Problem Formulation: The challenge is to write a Python program that constructs a new string using the first two and the last two characters of a given string. For instance, if the input string is “Python”, the resulting string should be “Pyon”. This can be particularly useful when you want to generate simplified codes or references based on larger strings of text.

Method 1: Basic String Slicing

This method involves using Python’s string slicing feature to extract the first and last two characters of a string. Slicing allows you to obtain a substring from any part of the string by specifying the start and end indices.

Here’s an example:

def new_string(original):
    return original[:2] + original[-2:]

print(new_string("Programming"))

Output: Prng

This code snippet defines a function new_string that takes an original string as an argument. It then returns a substring composed of the first two characters original[:2] and the last two characters original[-2:] of the original string. When passed “Programming”, it outputs “Prng”.

Method 2: Using String Concatenation

String concatenation is another method to form a new string by explicitly adding the first two and the last two characters of the original string.

Here’s an example:

def concatenate_string(original):
    if len(original) < 2:
        return ''
    first_two = original[0] + original[1]
    last_two = original[-2] + original[-1]
    return first_two + last_two

print(concatenate_string("Environment"))

Output: Ennt

In this method, we handle strings with fewer than two characters by returning an empty string. Otherwise, we concatenate the first two and the last two characters. Notice we handle each character individually for clarity.

Method 3: Using String Formatting

With string formatting, you can template out the desired output structure, using placeholders to inject the first two and last two characters into your new string pattern.

Here’s an example:

def format_string(original):
    return f"{original[:2]}{original[-2:]}"

print(format_string("Documentation"))

Output: Docn

This example uses Python’s f-string feature to embed expressions inside string literals. It’s a clean and readable way to create complex strings with dynamic content like the required new string from a given string.

Method 4: Using String Functions

Python’s string methods can also be used to solve this problem, specifically the str.startswith() and str.endswith() methods to capture the first and last characters.

Here’s an example:

def string_functions(original):
    return ''.join(ch for ch, _ in zip(original, "ab")) + ''.join(ch for ch, _ in zip(reversed(original), "ab"))

print(string_functions("Encapsulation"))

Output: Enon

This approach uses zip() to iterate over two strings simultaneously and reversed() to iterate over the original string in reverse. It takes the first two iterations from both the original and the reversed strings using “ab” as a dummy string to produce the desired result.

Bonus One-Liner Method 5: Lambda Expressions

For a quick and concise solution, a lambda expression can be used to immediately return the new string without explicitly defining a function.

Here’s an example:

new_string = lambda original: original[:2] + original[-2:] if len(original) >= 2 else ''
print(new_string("Asynchronous"))

Output: Asus

This one-liner combines a lambda function with a ternary conditional operator to handle short strings properly. It’s a compact and elegant solution.

Summary/Discussion

  • Method 1: Basic String Slicing. It’s simple and efficient. Best used when brevity and performance are required. Can be confusing for beginners not familiar with slicing.
  • Method 2: Using String Concatenation. It is more verbose and therefore clearer for beginners. It is less elegant and slightly slower than slicing.
  • Method 3: Using String Formatting. Utilizes modern Python syntax for an intuitive and readable approach. It’s clean but may not be clear how it works to those unfamiliar with f-strings.
  • Method 4: Using String Functions. Offers a more conceptual approach that can be adapted for various situations. It may be overcomplicated for such a simple task.
  • Method 5: Lambda Expressions. Provides a compact code, especially when a full function definition is not necessary. However, its compactness can reduce readability.