1. Python Basics: Variables, Strings, and Numbers

Variables are storage locations that have a name.

Variables and data types. Python provides several basic data types, including strings, integers, and floating-point numbers. Variables are created using the assignment operator (=) and can store any of these data types. Strings are enclosed in quotes and support various operations like concatenation and repetition.

String manipulation. Python offers built-in functions and methods for working with strings:

• len(): Returns the length of a string
• upper() and lower(): Convert strings to uppercase or lowercase
• format(): Allows for string interpolation
• Indexing and slicing: Access individual characters or substrings

Numeric operations. Python supports basic arithmetic operations (+, -, *, /) as well as more advanced operations like exponentiation (**) and modulo (%). The language also provides built-in functions for type conversion (int(), float(), str()) and mathematical operations (max(), min()).

2. Control Flow: Booleans, Conditionals, and Functions

Functions allow you to write a block of Python code once and use it many times.

Boolean logic. Python uses True and False as boolean values. Comparison operators (==, !=, >, <, >=, <=) and logical operators (and, or, not) are used to create boolean expressions.

Conditional statements. Control flow is managed using if, elif, and else statements:

• if condition:

  code block

• elif another_condition:

  code block

• else:

  code block

Functions. Functions are defined using the def keyword, followed by the function name and parameters. They can accept arguments, perform operations, and return values. Functions promote code reusability and organization.

3. Data Structures: Lists, Dictionaries, and Tuples

A list is a data type that holds an ordered collection of items.

Lists. Lists are mutable, ordered collections of items. They are created using square brackets [] and support various operations:

• Indexing and slicing
• append(), extend(), and insert() for adding items
• remove() and pop() for removing items
• sort() for sorting items

Dictionaries. Dictionaries are unordered collections of key-value pairs. They are created using curly braces {} and colons to separate keys and values. Dictionaries offer fast lookups and are useful for storing structured data.

Tuples. Tuples are immutable, ordered collections of items. They are created using parentheses () and are often used for fixed sets of data. While their contents cannot be changed after creation, tuples can be unpacked into multiple variables.

4. File Handling: Reading, Writing, and Modes

To open a file, use the built-in open() function.

Opening files. The open() function is used to open files, with various modes available:

• 'r': Read (default)
• 'w': Write (overwrites existing content)
• 'a': Append
• 'b': Binary mode

Reading and writing. Files can be read using methods like read(), readline(), or readlines(). Writing is done using the write() method. The with statement is recommended for automatically closing files after use.

File modes and error handling. Different file modes allow for various operations, such as reading, writing, or appending. It's important to handle potential errors when working with files using try/except blocks to catch exceptions like FileNotFoundError.

5. Modular Programming: Importing and Creating Modules

Python modules are files that have a .py extension and can implement a set of attributes (variables), methods (functions), and classes (types).

Importing modules. Modules can be imported using the import statement. Specific functions or attributes can be imported using from module import function. This allows for code reuse and organization.

Creating modules. Custom modules can be created by saving Python code in .py files. These modules can then be imported and used in other Python scripts. The name variable can be used to determine if a module is being run directly or imported.

Module search path. Python uses a search path to find modules. This path can be modified using the PYTHONPATH environment variable or by manipulating sys.path in the code.

6. Error Handling: Exceptions and Try/Except Blocks

An exception is typically an indication that something went wrong or something unexpected occurred in your program.

Types of exceptions. Python has many built-in exception types, such as ValueError, TypeError, and FileNotFoundError. These help identify specific issues in the code.

Try/except blocks. Exceptions can be caught and handled using try/except blocks:

try:
    # Code that might raise an exception
except ExceptionType:
    # Code to handle the exception

Custom exceptions. Programmers can create custom exception classes by inheriting from the built-in Exception class. This allows for more specific error handling in complex applications.

7. Python Standard Library: Built-in Modules and Functions

Python is distributed with a large library of modules that you can take advantage of.

Common standard library modules:

• time: For time-related functions
• sys: For system-specific parameters and functions
• os: For operating system interfaces
• json: For JSON encoding and decoding
• csv: For reading and writing CSV files
• random: For generating random numbers

Built-in functions. Python provides many built-in functions that are always available:

• print(): For output to the console
• input(): For user input
• len(): For getting the length of sequences
• range(): For generating sequences of numbers
• type(): For determining the type of an object

Exploring modules. The dir() function can be used to explore the contents of modules, showing available functions and attributes. The help() function provides detailed documentation for modules, functions, and objects.

Last updated: July 22, 2024