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Strings in Python

To understand Python strings and their role within data structures, we must look at how they are stored and manipulated in memory.

Definition & Characteristics​

In Python, strings are immutable sequences of Unicode characters. They can be defined using single (' '), double (" "), or triple quotes (''' '''). Because they are immutable, any modification to a string (like concatenation or replacement) results in the creation of a newly allocated string rather than changing the original one in place.

Internal Implementation​

Internally, Python strings are represented as dynamic arrays of Unicode characters. Depending on the characters used, Python optimizes the memory under the hood by choosing the most memory-efficient character representation (ASCII, UTF-8, etc.).

Common Operations & Methods​

Python strings support various operations, including slicing, concatenation, and a wide array of built-in methods.

# String definition
text = "Data Structures"

# Slicing
print(text[0:4])  # Output: Data

# Immutability check
# text[0] = "d" # This will raise a TypeError!

# Common Methods
print(text.lower())       # data structures
print(text.upper())       # DATA STRUCTURES
print(text.replace("Data", "Memory")) # Memory Structures

Applications of Strings​

Strings are fundamental in computer science and software development. Typical use cases include:

  • Plagiarism Checking: Using string matching algorithms (e.g., KMP, Rabin-Karp) to find similarities.
  • Encoding/Decoding: Converting data into a specific format for secure transmission or storage.
  • Text Processing & NLP: Tokenizing sentences, cleaning text, and building lexers for parsers.

Content sourced and adapted from GeeksforGeeks DSA with Python guides.