[Add]: Strings

Author: gauravfs-14

docs/python-basics/stings.md

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+---
+sidebar_position: 6
+---
+
+# Strings
+
+## Definition of a String
+
+- A **string** is a sequence of characters, essentially text data. In Python, a string is represented by enclosing characters within either **single** (`'`) or **double quotes** (`"`).
+- Example:
+  ```python title="strings.py"
+  name = "John"
+  greeting = 'Hello, world!'
+  ```
+
+## Creating Strings
+
+- Strings can be assigned to variables:
+  ```python title="strings.py"
+  city = "San Francisco"
+  ```
+- **Double vs. Single Quotes**:
+  - You can use both single or double quotes to create strings.
+  - The opening and closing quotes must match.
+  - Example:
+    ```python title="strings.py"
+    sentence = 'It\'s a sunny day'
+    # Alternatively, using double quotes avoids the need to escape the single quote:
+    sentence = "It's a sunny day"
+    ```
+
+## Multi-line Strings
+
+- For **multi-line strings**, use **triple quotes** (`'''` or `"""`).
+- Example:
+  ```python title="strings.py"
+  address = """123 Elm Street
+  Springfield
+  USA"""
+  ```
+- This allows the string to span multiple lines.
+
+## String Concatenation
+
+- You can **concatenate** (join) strings using the **`+` operator**:
+  ```python title="strings.py"
+  full_name = "John" + " " + "Doe"
+  # Output: "John Doe"
+  ```
+- Note that **spaces** between words must be explicitly added, as shown.
+
+## String Length
+
+- Use the **`len()` function** to get the length of a string:
+  ```python title="strings.py"
+  length = len(full_name)
+  print("Length of the full name:", length)
+  # Output: 8
+  ```
+
+## String Repetition
+
+- You can **repeat** a string using the `*` operator:
+  ```python title="strings.py"
+  dash_line = "-" * 5
+  # Output: "-----"
+  ```
+
+## String Methods
+
+- **`upper()`**: Converts all characters to uppercase.
+  ```python title="strings.py"
+  greeting = "hello"
+  print(greeting.upper())  # Output: "HELLO"
+  ```
+- **`lower()`**: Converts all characters to lowercase.
+  ```python title="strings.py"
+  print(greeting.lower())  # Output: "hello"
+  ```
+- **`title()`**: Converts the first character of each word to uppercase.
+  ```python title="strings.py"
+  title_greeting = "welcome to python"
+  print(title_greeting.title())  # Output: "Welcome To Python"
+  ```
+
+## Whitespace Removal
+
+- **`strip()`**: Removes leading and trailing whitespace.
+  ```python title="strings.py"
+  spaced_string = "  Hello  "
+  print(spaced_string.strip())  # Output: "Hello"
+  ```
+- **`lstrip()`**: Removes leading whitespace only.
+- **`rstrip()`**: Removes trailing whitespace only.
+
+## Replacing Substrings
+
+- **`replace(old, new)`**: Replaces all occurrences of `old` with `new` in the string.
+  ```python title="strings.py"
+  text = "I like apples"
+  new_text = text.replace("apples", "bananas")
+  print(new_text)  # Output: "I like bananas"
+  ```
+
+## Finding Substrings
+
+- **`count(sub)`**: Counts how many times a substring appears in the string.
+  ```python title="strings.py"
+  phrase = "banana"
+  print(phrase.count("a"))  # Output: 3
+  ```
+- **`find(sub)`**: Returns the index of the first occurrence of the substring. If not found, returns `-1`.
+  ```python title="strings.py"
+  print(phrase.find("na"))  # Output: 2
+  ```
+
+## Accessing Characters in a String
+
+- You can **access individual characters** in a string using **indexing** with square brackets.
+- **Index starts at `0`** (first character):
+  ```python title="strings.py"
+  first_char = phrase[0]  # Output: 'b'
+  ```
+- **Negative indexing** starts from the end:
+  ```python title="strings.py"
+  last_char = phrase[-1]  # Output: 'a'
+  ```
+
+## Comments and Disabling Code
+
+- Use the **`#` symbol** to add comments to your code.
+- Example:
+  ```python title="strings.py"
+  # This is a comment
+  print("Hello, World!")  # This line prints a greeting
+  ```
+- You can **comment out lines of code** to prevent them from executing, especially useful during debugging:
+  ```python title="strings.py"
+  # print("This line won't run")
+  print("This line will run")
+  ```
+
+## String Slicing
+
+- You can extract **substrings** using slicing syntax `[start:end]`:
+  ```python title="strings.py"
+  text = "Python programming"
+  sub_text = text[0:6]  # Output: "Python"
+  ```
+- **`start`** is inclusive, **`end`** is exclusive.
+
+This overview gives a foundational understanding of working with strings in Python, covering creating, manipulating, and accessing string data effectively.