Python Programming Fundamentals

Python Introduction

• Python is a dynamic, interpreted language that is bytecode-compiled
• One of the key features of Python is the absence of type declarations for variables, parameters, functions, or methods, allowing for a shorter and more flexible codebase
• Python tracks the types of all values at runtime
• Python was created by Guido van Rossum, in 1991
• Python is used for web development, software development, mathematics, and system scripting

Why Python?

• Python can be used across platforms like Windows, Mac, Linux, Raspberry Pi, etc
• Python's syntax is similar to the English language
• Developers can write programs with fewer lines
• Python runs on an interpreter system which allows code to be executed as soon as it is written
• Prototyping can be very quick since code is executed immediately
• Python can be treated in a procedural way, an object-oriented way, or a functional way
• Interpreters are used to run programs

Advantages of Python

• Python downloads with an extensive library containing code for regular expressions, documentation-generation, unit-testing, web browsers, threading, databases, CGI, email, and image manipulation
• Python can be extend to other languages and code can be written in C++ or C
• Python is easy to learn, understand, and code
• Complimenting extensibility, Python is embeddable as well
• Python code can be imbedded in a different language, like C++
• Python's simplicity and extensive libraries allow programmers to be more productive compared to languages like Java and C++
• Python forms the foundation of new platforms like Raspberry Pi, paving the way for the Internet Of Things
• Reading Python is like reading English
• Indentation is mandatory unlike other programming languages which use curly braces to define blocks
• Python supports procedural and object-oriented programming paradigms
• Classes allow the encapsulation of data and functions into one
• Python is freely available with downloadable source code and an extensive collection of libraries
• Python is portable, code only needs to be written once and can be run anywhere (Write Once Run Anywhere - WORA)
• Be careful not to include any system-dependent features when using WORA
• Debugging is easier in Python than in compiled languages, since statements are executed one by one

Uses of Python

• Python creates web applications
• Python creates software workflows
• Python connects to database systems, reading and modifying files
• Python handles big data and performs complex mathematics
• Python is used for rapid prototyping and production-ready software development

Introduction to Jupyter

• The Jupyter Notebook is an open-source web app for creating and sharing documents with live code, equations, visuals, and text.
• Anaconda is a Python distribution including the installer tool conda for third-party packages
• Anaconda comes with scientific libraries pre-installed like the Jupyter Notebook allowing users to install Anaconda

Jupyter Notebooks

• A Notebook's cell defaults to using chosen kernel code. Initial Notebooks have one empty cell.
• To verify code, add Python code to the cell and run it.

Data types

• Data types classify or categorize data items, defining how to operate on particular data
• In Python, data types are classes due to object-oriented programming, with variables as class instances

Basic Types of data

• Numeric
• Dictionary
• Set
• Boolean
• Sequence Type

Integer

• In Python, integer value length is effectively unlimited, constrained only by system memory

Float

• Float types designates a floating-point number using a decimal point for specification
• The character e or E may be used followed by an option positive or negative integer to denote usage of scientific notation for float values

String

• Strings are arrays of bytes representing unicode characters
• A string is a collection of one or more characters put in a single quote, double quote, or triple quote
• Characters lack unique data types; strings of length one represent them, found in str class

Type Function

• Function type() determines a data type

Boolean

• Boolean datatypes may have one of two values, True or False.

Type Casting

• Type Casting converts variable data types for operations
• Two types of Type Casting are, Implicit and Explicit

Implicit Type Casting

• Python automatically converts data types without user involvement

Explicit Type Casting

• Explicit Type Casting requires involvement to convert variable data types using these functions to cast
• int(): Takes float or string args, returns int object
• float(): Takes int or string args, returns float object
• str(): Takes float or int args, returns string object

Type casting

• Casting an integer object to a float object is done with the float() function
• Casting float data types in integer data types uses the int() function
• Casting int data types to string data types uses the str() function

Arithmetic Operators

• Arithmetic operators are used with numeric values to perform common mathematical operations:
• Addition: x + y
• Subtraction: x - y
• Multiplication: x * y
• Division: x / y
• Modules: x % y
• Exponentiation: x ** y
• Floor division: x // y

Assignment Operators

• Assignment operators values to variables
• x = 5, x = 5
• x += 3, x = x + 3
• x -= 3, x = x - 3
• x *= 3, x = x * 3
• x /= 3, x = x / 3
• x %= 3, x = x % 3
• x //= 3, x = x // 3
• x **= 3, x = x ** 3

Assignment Operator

• x &= 3 is the same as x = x & 3
• x != 3 is the same as x = x | 3
• x ^= 3 is the same as x = x ^ 3
• x >>= 3 is the same as x = x >> 3
• x <<= 3 is the same as x = x << 3

Comparison Operator

• Double equals == is equal to
• Exclamation Mark != is not equal to
• Greater than >
• Less than <
• Greater than or equal to >=
• Less than or equal to <=

Logical Operator

• Logical operators are use to combine conditional statements

Logical Operator definitions

• and: returns True if both statements are true
• or: returns True if one of the statements is true
• not: reverses a result, returns false if the result is true

Identity Operator

• Identity operators ensure the the objects are identical with the same memory allocation
• is: Returns True if both variables are the same object
• is not: Returns True if both variables are not the same object

Memebership Operator

• Membership operators test for a sequence presented in an object
• in: returns True if a sequence with a specified value is present in the object
• not in: returns True if a sequence with a specified value is not present in the object

Bitwise Operators

• Bitwise operators compare binary numbers
• &: AND sets each bit to 1 if both bits are 1
• |: OR sets each bit to 1 if one of two bits is 1
• ^: XOR sets each bit to 1 if only one of two bits is 1
• ~: NOT inverts all the bits
• <<: Zero fill left shift shifts left by pushing zeros in from the right, letting leftmost bits fall off

• : Signed right shift shifts right by pushing leftmost bit copies from the let, letting rightmost bits fall off

Ternary Operator

• Ternary operators are also known as conditional expressions evaluating something based on being true or false
• Ternary operators allow testing a condition in a single line replacing multiline if-else making the code compact

Operator Precedence

• Parentheses () have left-to-right associativity
• Exponent ** has right-to-left associativity
• Multiplication * Division / Modulus % have left-to-right associativity
• Addition + Subtraction - have left-to-right associativity
• Bitwise shift left << Bitwise shift right >> have left-to-right associativity
• Relational < <= Relational > >= have left-to-right associativity
• Relational == != have left-to-right associativity
• Identity is, is not has left-to-right associativity
• Membership operators in, not in has left-to-right associativity
• Bitwise AND & has left-to-right associativity
• Bitwise exclusive OR ^ has left-to-right associativity
• Bitwise inclusive NOR | has left-to-right associativity
• Logical NOT not has right-to-left associativity
• Logical AND and has left-to-right associativity
• Logical OR or has left-to-right associativity
• Assignment =, +=, -=, *=, /=, %=, //=, **= have right-to-left associativity
• Bitwise exclusive/inclusive OR assignment ^= |=
• Bitwise shift left/right assignment <<= >>=

Basic Programming Style of Python

• Functional treats every statement as a mathematical equation avoiding state or mutable data, lends itself to parallel processing, and is preferred for recursion and lambda calculus
• Imperative performs computation as direct change to program state, especially useful in data structure manipulation with implementation using Python
• Object-oriented relies on data fields manipulated through prescribed methods, not fully supported by Python, and favors code reuse
• Procedural treats tasks as step-by-step iterations utilizing functions for common tasks with sequencing, selection, and modularization

Memory allocation

• Memory allocation in Python consists of two parts which are Stack and Heap memory
• Stack memory stores the references and method/method calls, while heap memory store the values objects

Stack Memory

• Stack memory happens on contiguous blocks of memory, called stack memory allocation, happening in the function call stack
• The compiler knows the size, and when calling a function, variables allocate memory to stack
• Inside a function or method call memory needed is available and functions are added onto program's stack

Heap Memory

• Local memory assignments and variable initializations inside functions are temporarily store on the call stack, deleting after function returns and the stack moves to the next task
• Allocation onto a contiguous block of memory uses predefined routines that do not require developers worries

Heap Memory details

• Occurs when executing instructions written by programmers
• Heap is unrelated to the heap data structure, rather a heap of memory space available for allocation and deallocation
• Global variables needed and shared across function code are stored in Heap momory

Indentation

• Python relies on indentation which is a white space at the beginning of a line
• Indentation defines scope in code
• Other languages use curly-brackets

Simple if Statement

• Simple if statements uses the keyword if

If Else Statement

• It uses the if keyword
• The else keyword catches preceding conditions that are incomplete

If Elif Else Statement

• The elif keyword combines if the previous conditions were not true, then uses current condition

Nested If

• If statements can be used, inside if statements

Short Hand If

• Allows if statments to be nested within if statments

Short Hand If Else

• Assigning one statement to execute within if and else can be stated on one single line
• It is called Ternary Operators

For Loop

• Designed to repeatedly execute a code block while iterating through a list, tuple, dictionary, or other iterable objects in Python
• Python traversal of sequence is iteration:
• for value in sequence:

•   {code block}
  

Using Else Statement with loop

• After sequence is complete, statement appears after for is executed
• The else statement only takes play once the execution is complete, and won't be executed if we exit the loop or if an error is thrown

While Loop

• Iterates until a specified condition is met
• The statement in the program that follows the while loop is executed once the condition changes to false
• while :
• {code block}

Using Else Statement with While Loops

• Can be used with while loop, syntax same

Single Statement While Block

• Loops declare in single statements, similar to if-else

The range() Function

• Produces a series of numbers, with a specified range with range(10) will produce values between 0 and 9, (10 numbers).
• Specific start, stop, and set size ranges can be range(start, stop, step size)
• The step size has a default 1 if it is not specified

For Loop Using range() Function

• Loops in range can be expressed as

Continue Statement

• Returns control to the beginning of a loop. If x == 10:
• Syntax: continue print(x)

Break Statement

• When activated, the loop's execution halts.
• loop {
• Condition: break
• }

Pass statment

• Pass statement creates empty loops, classes, functions and empty control statements

Explore Python characteristics, operators, and memory management. Learn about its 'Write Once Run Anywhere' capability and suitability for diverse applications. Understand Python's role as a dynamic, interpreted language.