Python Data Types

Data Types

• Numeric Types:
  • Int: whole numbers, e.g., 1, 2, 3
  • Float: decimal numbers, e.g., 3.14, -0.5
  • Complex: complex numbers, e.g., 3+4j, 4-2j
• Sequence Types:
  • String: sequence of characters, e.g., "hello", 'hello'
  • List: ordered collection of items, e.g., [1, 2, 3], ["a", "b", "c"]
  • Tuple: ordered, immutable collection of items, e.g., (1, 2, 3), ("a", "b", "c")
• Mapping Type:
  • Dictionary: unordered collection of key-value pairs, e.g., {"name": "John", "age": 30}
• Set Types:
  • Set: unordered collection of unique items, e.g., {1, 2, 3}, {"a", "b", "c"}
  • Frozenset: unordered, immutable collection of unique items, e.g., frozenset([1, 2, 3])

Control Structures

• Conditional Statements:
  • If: executes a block of code if a condition is true
  • Elif: executes a block of code if a condition is true (used with if)
  • Else: executes a block of code if all conditions are false
• Loops:
  • For: executes a block of code for each item in an iterable
  • While: executes a block of code while a condition is true
• Jump Statements:
  • Break: exits a loop or switch statement
  • Continue: skips the current iteration of a loop
  • Pass: does nothing, used as a placeholder
  • Return: exits a function and returns a value

Object-oriented Programming

• Classes:
  • Define a blueprint for creating objects
  • Can have attributes (data) and methods (functions)
• Objects:
  • Instances of classes
  • Have their own attributes and methods
• Inheritance:
  • A child class can inherit attributes and methods from a parent class
  • Can also override or extend parent class attributes and methods
• Polymorphism:
  • Objects of different classes can be treated as objects of a common superclass
  • Methods can be overridden or overloaded to provide different behavior

File Input/Output

• Reading Files:
  • open() function: opens a file and returns a file object
  • read() method: reads the contents of a file
  • readline() method: reads a single line from a file
  • readlines() method: reads all lines from a file
• Writing Files:
  • open() function: opens a file and returns a file object
  • write() method: writes to a file
  • writelines() method: writes a list of strings to a file
• Modes:
  • r mode: read-only mode
  • w mode: write-only mode (truncates the file if it exists)
  • a mode: append-only mode
  • r+ mode: read and write mode
  • b mode: binary mode (for reading and writing binary files)

Data Types

• Numeric Types:
  • Integers are whole numbers, e.g., 1, 2, 3.
  • Floats are decimal numbers, e.g., 3.14, -0.5.
  • Complex numbers are represented as a + bj, where a and b are floats and j is the imaginary unit, e.g., 3+4j, 4-2j.
• Sequence Types:
  • Strings are sequences of characters, e.g., "hello", 'hello'.
  • Lists are ordered collections of items, e.g., [1, 2, 3], ["a", "b", "c"].
  • Tuples are ordered, immutable collections of items, e.g., (1, 2, 3), ("a", "b", "c").
• Mapping Type:
  • Dictionaries are unordered collections of key-value pairs, e.g., {"name": "John", "age": 30}.
• Set Types:
  • Sets are unordered collections of unique items, e.g., {1, 2, 3}, {"a", "b", "c"}.
  • Frozensets are unordered, immutable collections of unique items, e.g., frozenset([1, 2, 3]).

Control Structures

• Conditional Statements:
  • If statements execute a block of code if a condition is true.
  • Elif statements execute a block of code if a condition is true, used with if statements.
  • Else statements execute a block of code if all conditions are false.
• Loops:
  • For loops execute a block of code for each item in an iterable.
  • While loops execute a block of code while a condition is true.
• Jump Statements:
  • Break statements exit a loop or switch statement.
  • Continue statements skip the current iteration of a loop.
  • Pass statements do nothing, used as a placeholder.
  • Return statements exit a function and return a value.

Object-oriented Programming

• Classes:
  • Classes define a blueprint for creating objects.
  • Classes can have attributes (data) and methods (functions).
• Objects:
  • Objects are instances of classes.
  • Objects have their own attributes and methods.
• Inheritance:
  • Child classes can inherit attributes and methods from parent classes.
  • Child classes can also override or extend parent class attributes and methods.
• Polymorphism:
  • Objects of different classes can be treated as objects of a common superclass.
  • Methods can be overridden or overloaded to provide different behavior.

File Input/Output

• Reading Files:
  • The open() function opens a file and returns a file object.
  • The read() method reads the contents of a file.
  • The readline() method reads a single line from a file.
  • The readlines() method reads all lines from a file.
• Writing Files:
  • The open() function opens a file and returns a file object.
  • The write() method writes to a file.
  • The writelines() method writes a list of strings to a file.
• Modes:
  • The r mode is read-only mode.
  • The w mode is write-only mode, truncating the file if it exists.
  • The a mode is append-only mode.
  • The r+ mode is read and write mode.
  • The b mode is binary mode for reading and writing binary files.