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Python

Basics of Python

Installing Python Setting up a Development Environment Writing and Running Your First Python Program Python's Syntax and Indentation

Variables and Data Types

Variables in python Numeric Data Types (int, float) Text Data Type (str) Boolean Data Type (bool) Type Conversion (Casting) Dynamic Typing in Python

Control Flow

Conditional Statements (if, elif, else) Comparison Operators Logical Operators Loops (for and while) Loop Control Statements (break and continue)

Functions

Defining Functions Function Parameters and Arguments Return Statements Scope and Lifetime of Variables Lambda Functions Recursion

Data Structures

Lists and List Operations Dictionaries and Dictionary Operations Tuples Sets List Comprehensions Dictionary Comprehensions

File Handling

Opening and Closing Files Reading and Writing Text Files Handling Exceptions in File Operations

Modules and Libraries

Importing Modules Commonly Used Standard Libraries External Libraries: NumPy and Pandas Installing and Managing Libraries with pip

Error Handling

Exceptions in Python Handling Exceptions with try and except Custom Exceptions
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Text Data Type (str)

Text Data Type (str)

In Python, the str data type is used to represent text, characters, and strings. Text data is essential for working with textual information, including messages, documents, and user input. In this section, we'll explore how to work with text data using the str type.

1. Creating String Variables

You can create string variables by enclosing text within single (' ') or double (" ") quotes. Both approaches are valid, and you can choose the one that suits your needs:

# Using single quotes
name = 'Alice'

# Using double quotes
greeting = "Hello, World!"

2. String Concatenation

Strings can be combined or concatenated using the + operator:

first_name = 'John'
last_name = 'Doe'

full_name = first_name + ' ' + last_name  # 'John Doe'

3. String Length

To determine the length of a string, you can use the len() function:

message = "This is a sample message"
length = len(message)  # 24

4. Accessing Characters

You can access individual characters within a string by their index. The first character has an index of 0:

text = "Python"
first_character = text[0]  # 'P'
second_character = text[1]  # 'y'

5. Slicing Strings

You can extract a portion of a string, known as a slice, using the [start:stop] notation:

text = "Python Programming"
substring = text[7:18]  # 'Programming'

6. String Methods

Python provides numerous built-in string methods for various operations. Here are some common string methods:

  • upper(): Converts a string to uppercase.
  • lower(): Converts a string to lowercase.
  • strip(): Removes leading and trailing whitespace.
  • replace(old, new): Replaces occurrences of a substring with another.
  • split(delimiter): Splits a string into a list of substrings based on a delimiter.
text = "Hello, World!"

uppercase_text = text.upper()  # 'HELLO, WORLD!'
lowercase_text = text.lower()  # 'hello, world!'
stripped_text = text.strip()  # 'Hello, World!'
replaced_text = text.replace("Hello", "Hi")  # 'Hi, World!'
words = text.split(", ")  # ['Hello', 'World!']

7. String Formatting

You can format strings using placeholders and the format() method:

name = "Alice"
age = 30

formatted_string = "My name is {} and I am {} years old.".format(name, age)
# 'My name is Alice and I am 30 years old.'

Alternatively, you can use f-strings (formatted string literals) to embed expressions inside string literals:

formatted_string = f"My name is {name} and I am {age} years old."
# 'My name is Alice and I am 30 years old.'

Understanding how to work with text data is crucial for various Python applications, such as text processing, user interfaces, and data manipulation. In the following sections, we'll explore more string-related operations and concepts.

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