Python Data Structures Lists and Tuples

Data Structures

Lists

• A collection of items that can be of any data type, including strings, integers, floats, and other lists
• Denoted by square brackets [] and elements are separated by commas
• Indexing starts at 0, and negative indices count from the end of the list
• Slicing: list[start:stop:step] returns a new list with elements from start to stop-1 with a step size of step

Tuples

• Similar to lists, but immutable (cannot be changed after creation)
• Denoted by round brackets () and elements are separated by commas
• Useful for storing a collection of values that shouldn't be changed

Dictionaries

• A collection of key-value pairs, where keys are unique strings and values can be of any data type
• Denoted by curly braces {} and elements are separated by commas
• Keys are used to access and manipulate values

Sets

• An unordered collection of unique elements, often used for fast membership testing
• Denoted by curly braces {} and elements are separated by commas
• Use the set() function to create a set from a list or other iterable

Exception Handling

Try-Except Block

• Used to catch and handle exceptions (errors) that occur during execution
• Syntax: try: ... except ExceptionType: ...
• The try block contains code that might raise an exception, and the except block contains code to handle the exception

Raising Exceptions

• Use the raise statement to raise a custom exception
• Syntax: raise ExceptionType("Error message")

Built-in Exceptions

• TypeError: raised when an operation is applied to an object of an incorrect type
• ValueError: raised when an operation is applied to an object with an incorrect value
• IOError: raised when an input/output operation fails
• SyntaxError: raised when there is a syntax error in the code

File Input/Output

Reading Files

• Use the open() function to open a file in read mode ('r')
• The read() method returns the entire contents of the file as a string
• The readlines() method returns a list of strings, where each string is a line in the file

Writing Files

• Use the open() function to open a file in write mode ('w')
• The write() method writes a string to the file
• The writelines() method writes a list of strings to the file

Modes

• 'r': read mode (default)
• 'w': write mode (overwrites existing file)
• 'a': append mode (adds to the end of the file)
• 'r+': read and write mode
• 'b': binary mode (used for files that contain non-text data)

Context Manager

• Use the with statement to open a file, ensuring it is properly closed when done
• Syntax: with open('filename', 'mode') as file: ...

Data Structures

Lists

• Lists are collections of items that can be of any data type, including strings, integers, floats, and other lists.
• Lists are denoted by square brackets [] and elements are separated by commas.
• Indexing in lists starts at 0, and negative indices count from the end of the list.
• Slicing in lists uses the format list[start:stop:step] and returns a new list with elements from start to stop-1 with a step size of step.

Tuples

• Tuples are similar to lists, but they are immutable, meaning they cannot be changed after creation.
• Tuples are denoted by round brackets () and elements are separated by commas.
• Tuples are useful for storing a collection of values that should not be changed.

Dictionaries

• Dictionaries are collections of key-value pairs, where keys are unique strings and values can be of any data type.
• Dictionaries are denoted by curly braces {} and elements are separated by commas.
• Keys are used to access and manipulate values in dictionaries.

Sets

• Sets are unordered collections of unique elements, often used for fast membership testing.
• Sets are denoted by curly braces {} and elements are separated by commas.
• The set() function can be used to create a set from a list or other iterable.

Exception Handling

Try-Except Block

• Try-except blocks are used to catch and handle exceptions (errors) that occur during execution.
• The syntax for a try-except block is try:...except ExceptionType:....
• The try block contains code that might raise an exception, and the except block contains code to handle the exception.

Raising Exceptions

• The raise statement is used to raise a custom exception.
• The syntax for raising an exception is raise ExceptionType("Error message").

Built-in Exceptions

• TypeError is raised when an operation is applied to an object of an incorrect type.
• ValueError is raised when an operation is applied to an object with an incorrect value.
• IOError is raised when an input/output operation fails.
• SyntaxError is raised when there is a syntax error in the code.

File Input/Output

Reading Files

• The open() function is used to open a file in read mode ('r').
• The read() method returns the entire contents of the file as a string.
• The readlines() method returns a list of strings, where each string is a line in the file.

Writing Files

• The open() function is used to open a file in write mode ('w').
• The write() method writes a string to the file.
• The writelines() method writes a list of strings to the file.

Modes

• 'r' is the read mode (default).
• 'w' is the write mode (overwrites existing file).
• 'a' is the append mode (adds to the end of the file).
• 'r+' is the read and write mode.
• 'b' is the binary mode (used for files that contain non-text data).

Context Manager

• The with statement is used to open a file, ensuring it is properly closed when done.
• The syntax for using a context manager is with open('filename', 'mode') as file:....

Understand the basics of data structures in Python, including lists and tuples. Learn how to work with these fundamental data types and their properties.