String Data Type in Python

String Data Type in Python

• Strings are a sequential collection of characters such as alphabets, digits, special characters, and spaces.
• In Python, strings are represented using inverted commas.
• Strings are immutable - once they are created they cannot be changed.

String Indexing

• Each character in a string has an index, starting from 0 for the first character.
• Forward indexing works from the beginning (0) to the end (len(string)-1) of the string.
• Backward indexing works from the end (-1) to the beginning (-length of string), making it easier to access the last character.

String Operations

• Concatenation: Joining two or more strings, denoted by the + operator.
• Repetition: Repeating a string multiple times, denoted by the * operator.
• Membership: Checking if a substring is present within a string, using the in or not in operators.
• Slicing: Extracting a portion of a string using indexing, specifying the start and end positions with optional step value.
• Traversing: Accessing each character in a string using a loop, for example a for loop, to perform operations on individual characters.

Built-in String Functions

• len(string): Returns the length of the string (number of characters).
• string.find('substring'): Returns the index of the first occurrence of the substring in the string.
• string.capitalize(): Converts the first character of the string to uppercase.
• string.lower(): Converts the string to lowercase.
• string.upper(): Converts the string to uppercase.
• string.lstrip(): Removes leading whitespace characters from the left side of the string.
• string.partition('separator'): Splits the string into a list based on the separator, providing the part before, the separator, and the part after.
• string.split('separator'): Splits the string into a list based on the separator.
• string.split(): Splits the string into a list using the default whitespace as a separator.
• string.isnumeric(): Checks if a string contains only numeric characters

Key Concepts

• Immutable: Strings are immutable, so once a string is created, you cannot modify its individual characters directly.
• Case Sensitivity: Python is case-sensitive, so the lowercase and uppercase characters are treated differently.

Example Code Review

• The code example demonstrates several String operations:
  • len(string) - to find the length of a string.
  • String slicing
  • String repetition
  • string.find('substring') - to find the index of a specific substring.
  • string.isnumeric() to check if a string contains only numeric characters.
  • string.upper() and string.lower() - to convert string to uppercase and lowercase respectively.
  • string.split('separator') - to split a string into a list based on a specified separator.

Practice Questions

• Understanding string indexing for accessing specific characters in a string.
• Applying string functions to perform various manipulations such as finding a substring, converting cases, and splitting the string.
• Understanding the concept of immutability and its impact on string operations.