Python Basics

• Python is a high-level, interpreted, interactive, and object-oriented scripting language designed for readability, using English keywords and fewer syntactical constructions.

Python Features

• Interpreted: Python is processed at runtime by the interpreter, similar to PERL and PHP, negating the need to compile your program before executing it.
• Interactive: Python enables direct interaction with the interpreter to write programs.
• Object-Oriented: Python supports Object-Oriented programming, which encapsulates code within objects.
• Beginner's Language: Python is suited for beginner-level programmers and supports a wide array of applications.

History

• Guido van Rossum developed Python in the late eighties and early nineties at the National Research Institute for Mathematics and Computer Science in the Netherlands.
• Python is derived from languages like ABC, Modula-3, C, C++, Algol-68, SmallTalk, and Unix shell.
• Python is copyrighted, with source code available under the GNU General Public License (GPL).
• A core development team at the institute currently maintains Python, with Guido van Rossum still playing a vital role.
• Python's Timeline:
  • Late 80s: Conceived
  • Dec 1989: Started implementation
  • Feb 1991: Released Python 0.9
  • Jan 1994: Released Python 1.0
  • Oct 2000: Released Python 2.0
  • Dec 2008: Released Python 3.0
  • Jun 2018: Released Python 3.7

Python's Key Features

• Easy-to-learn: Few keywords, simple structure, and a clearly defined syntax allow quick language acquisition.
• Easy-to-read: Python code is clearly defined and visible.
• Easy-to-maintain: Python's source code is fairly easy to maintain.
• Broad standard library: The library is portable and cross-platform compatible on UNIX, Windows, and Macintosh.
• Interactive Mode: Interactive mode enables interactive testing/debugging.
• Portable: Python runs on various hardware platforms with the same interface.
• Extendable: Low-level modules can be added to the Python interpreter to customize tools.
• Databases: Python provides interfaces to commercial databases.
• GUI Programming: Python supports GUI applications that can be ported to various systems.
• Scalable: Python provides better structure/support for large programs than shell scripting.

Advantages

• Python is a high-level programming language with English-like syntax, making it easy to read and understand.
• Python enhances productivity due to its simplicity.
• Python is an interpreted language that executes code line by line.
• Python automatically assigns data types during execution because it is dynamically typed. Programmers don't have to declare variable types.
• Python is free to use and distribute under the OSI-approved open-source license.
• Python offers vast library support, reducing dependency on external libraries.
• Portability of Python means it only needs to be written once to run anywhere.

Running Python Scripts

• A Python script is a file containing Python code or a program that ends with a .py extension.
• An interpreter can execute a script as a module or as a script itself.
• Code can be written in an interactive Python command prompt session.

Running Python Code Interactively

• Open the command line in interactive mode.
• Invoke the Python interpreter in the command line.
• Sequentially write and execute Python code.
• Can exit the windows command line by pressing Ctrl+Z and following with an Enter.
• Python script files can end with either .py or .pyw.

Running Scripts via Jupyter Notebook

• Download the Python installer, available on the Continuum Analytics website.
• Note that the installer is larger than average, and should include Python, packages, code editor, and other gadgets.

Installing Anaconda/Python

• Double click the .exe (Windows) or .pkg (Mac) file after downloading the graphical installer, then follow the on-screen instructions.
• Steps for installing/uninstalling Python are available online.
• When installing Anaconda, a pop-up menu may ask whether to “Add Anaconda to my PATH environment variable” and “Register Anaconda as my default Python 3.5."

Starting Jupyter Notebook

• After downloading/installing Anaconda, find associated tools to open Jupyter Notebook.
• Access the tools via the Anaconda folder from the Start menu (Windows only) or the Anaconda Navigator shortcut icon.

Variables

• Variables are reserved memory locations for storing values, implying memory allocation upon creation.
• The interpreter allocates memory based on the variable's data type.
• Variables can store integers, decimals, or characters by assigning different data types.

Variable Creation Rules

• Variables must start with a letter or the underscore character.
• Variables cannot start with a number.
• Variables can only contain alpha-numeric characters and underscores (A-z, 0-9, and _).
• Variable names are case-sensitive (name, Name, NAME are distinct).
• Reserved words or keywords cannot be used as variable names.

Assigning Values

• Explicit variable declaration to reserve memory space is unnecessary.
• Declaration happens automatically upon assigning a value to a variable, using the equal sign (=).
• The operand to the left of = is the variable name, and the operand to the right is the value stored.

Assignment Types

• Multiple Assignment: Assign a single value to multiple variables simultaneously.
• Multiple Objects: Assign multiple objects to multiple to variables.

Standard Python Data Types

• Data stored in memory can be numeric, alphanumeric, etc.
• Standard data types in Python define the operations possible and the storage method for each.
• Python Standard Data Types include Numbers, String, List, Tuple, Dictionary and Boolean. Set is also a Python Standard Data Type.

Python Numbers

• Number data types store numeric values; objects created upon assignment.
• Can delete single or multiple objects using the statement del.
• Supports int, long, float, and complex number types.

Python Strings

• Strings are contiguous sets of characters in quotation marks, allowing single or double quotes.
• Subsets of strings use the slice operator ([ ] and [:]) with indexes starting at 0.
• The plus (+) sign is the string concatenation operator; the asterisk (*) is the repetition operator.

String Operators

• Strings are created by enclosing characters in quotes and are a popular type in Python.
• Python treats single/double quotes the same.
• String creation is simple and involves assigning a value to a variable.

Accessing Values

• Python treats characters as strings of length one.
• Substrings are accessed via square brackets for slicing with index/indices.

Updating Strings

• Assigning a variable to another string is how strings are updated.
• The new value can relate to its previous value or be a different string altogether.

String Special Operators

• Assume variable a holds 'Hello' and variable b holds 'Python':: -+ Concatenation - Adds values on either side of the operator: a + b will give HelloPython -* Repetition - Creates new strings, concatenating multiple copies of the same string: a*2 will give HelloHello -[] Slice - Gives the character from the given index: a[1] will give e -[:] Range Slice - Gives the characters from the given range: a[1:4] will give ell -in Membership - Returns true if a character exists in the given string: H in a will give 1 -not in Membership - Returns true if a character does not exist in the given string: M not in a will give 1 -r/R Raw String - Suppresses actual meaning of Escape characters: print r'\n'prints \n and print R'\n'prints \n

Triple Quotes

• Enable strings to span multiple lines, including NEWLINEs, TABs, etc.
• Consists of three consecutive single/double quotes.

Built-in String Methods

• Manipulate strings in Python using built-in methods.
  • capitalize(): Capitalizes the first letter of string.
  • center(width, fillchar): Returns a space-padded string with the original string centered to a total of width columns.
  • count(str, beg= 0,end=len(string)): Counts how many times str occurs in string or in a substring of string if starting index beg and ending index end are given.
  • decode(encoding='UTF-8',errors='strict'): Decodes the string using the codec registered for encoding.
  • encode(encoding='UTF-8',errors='strict'): Returns encoded string version of string; Unless errors is given with 'ignore' or 'replace' a Value Error is raised if there is an error.
  • endswith(suffix, beg=0, end=len(string)): Determines if string (or substring with specified indices) ends with suffix; returns true if so.
  • expandtabs(tabsize=8): Expands tabs in string to multiple spaces and defaults to 8 spaces per tab.
  • find(str, beg=0 end=len(string)): Identifies if str occurs in string or if a string of str occurs in a substring - returns index if found and -1 if it is missed.
  • index(str, beg=0, end=len(string)): Same as find(), but raises an exception if str not found.
  • isalnum(): Returns true if string has at least 1 character and all characters including alphanumeric and false if this is missed.
  • isalpha(): Returns true if string has at least 1 character and all characters including alphabetic and false if this is missed.
  • isdigit(): Returns true if string contains only digits and false otherwise.
  • islower(): Returns true if string has at least 1 cased character and all cased characters are in lowercase, and the function returns false if this is missed.
  • isnumeric(): Returns true if a unicode string contains only numeric characters.
  • isspace(): Returns true if string contains only whitespace characters and returns false if this is missed.
  • istitle(): Returns true if string is properly "titlecased" and false otherwise.
  • isupper(): Returns true if string has at least one cased character and all cased characters are in uppercase.
  • join(sep): Merges, concatenates, the string representations of elements in sequence seq into a string, with separator string.
  • len(string): Returns the length of the string.
  • ljust(width[, fillchar]): Returns a space-padded string with the original string left-justified to a total of width columns.
  • lower(): Converts all uppercase letters in string to lowercase.
  • lstrip(): Removes all leading whitespace in string.
  • maketrans(): Returns a translation table to be used in translate function.
  • max(str): Returns the max alphabetical character from the string str.
  • min(str): Returns the min alphabetical character from the string str.
  • replace(old, new [, max]): Replaces all occurrences of old in string with new or at most max occurrences if max given.

Mathematical Operators

• Manipulate the value of operands and are constructs that you can use.
• 4 + 5 = 9 Here, 4 and 5 are the operands and + is the operator.

Operator Types

• Arithmetic.
• Comparison (Relational).
• Assignment.
• Logical.
• Bitwise.
• Membership.
• Identity.

Python arithmetic operators

• Assume variable a holds 10 and variable b holds 20: -+Addition: Adds values on either side of the operator: a + b = 30 -- Subtraction: Subtracts right hand operand from left hand operand: a - b = - 10 -Multiplication: Multiplies values on either side of the operator: a b = 200 -/Division: Divides left hand operand by right hand operand: b/a = 2 -% Modulus: Divides left hand operand by right hand operand and returns remainder: b%a = 0 -** Exponent: Performs exponential calculation on operators: a**b =10 to the power 20 -//Floor Division: The division of operands where the result is the quotient in which the digits after the decimal point are removed. But if one of the operands is negative, the result is floored: 9//2 = 4 and 9.0//2.0 = 4.0, - 11//3 =-4, - 11.0//3 =-4.0

Python Comparison Operators

• Used to compare the values on either sides of them and decide on the relation between them.
• Are also called relational operators.

Python Assignment Operators

• Assume variable a holds 10 and variable b holds 20: -= Assigns values from right side operands to left side operand: c = a + b assigns value of a + b into c -+= Add AND Adds right operand to the left operand and assign the result to left operand: c += a is equivalent to c = c + a --= Subtract AND: It subtracts right operand from the left operand and assign the result to left operand c -= a is equivalent to c = c - a -*= Multiply AND: It multiplies right operand with the left operand and assign the result to left operand c *= a is equivalent to c = c * a -/= Divide AND: It divides left operand with the right operand and assign the result to left operand: c /= a is equivalent to c = c / a -%= Modulus AND: It takes modulus using two operands and assign the result to left operand: c %= a is equivalent to c = c % a -**= Exponent AND: Performs exponential calculation on operators and assign value to the left operand: c **= a is equivalen t to c = c ** a -//= Floor Division: It performs floor division on operators and assign value to the left operand: c //= a is equivalent to c = c // a

Python Bitwise Operators:

• Bitwise operator works on bits , and performs operation bit by bit.
• There are following Bitwise operators supported by Python language: -& Binary AND: Operator copies a bit to the result if it exists in both operands. -| Binary OR: It copies a bit if it exists in either operand. -^ Binary XOR: It copies the bit if it is set in one operand but not both. -~Binary Ones Complement: Is unary and has the effect of flipping’ bits. -<< Binary Left Shift: The left operands value is moved left by the number of bits specified by the right operand. ->> Binary Right Shift: The left operands value is moved right by the number of bits specified by the right operand.

Python Logical Operators

• Supported by program language.
• AND: If both the operands are true then condition becomes true.
• OR: If any of the two operands are non-zero then condition becomes true.
• NOT: Used to reverse the logical state of its operand.

Identity Operators

• Help to check if the operands share the same memory location

Membership Operators

• Help to check if there is a member in a sequence - such a character within a string

Input Function

• The input() function is used to take user input from the keyboard.
• In Python 3, the input() function has been modified. The old raw_input() from Python 2 was removed.

Indentation

• Indentation can be done with whitespace, such as blank spaces or tabs.
• Helps define a block of code.
• In Python, the blocks of code are highlighted with indentation.

Conditional Statements

• Also called decision-making statements.
• Used while trying to execute a block of code and check if the given condition is true or false.
• Types include if, if else, Elif and Nested if:
  • if statement: Used to check a condition and execute a block of code if the condition is true. Is the primary conditional statement and can be used alone or in conjunction with else or elif. If the condition in the if statement is true, the associated block of code is executed, and then the program moves on to the next part.
  • elif statement: Is used to check additional conditions if the previous if or elif conditions were not true and is an abbreviation for "else if."

Loop Statements

• Enable the the repeated execution of a block of code.
  • While loop: a set of statements can be executed in these loops, as long as their condition is true.
  • For loop: these loops iterate through items in a sequence.

Breaking and Continuing Loops

• Break loop: Stop the loop even if the while condition is true.
• Continue loop: Stop the current iteration, and continue with the next.

Nested Loops

• Referred to when a loop becomes a loop inside a loop.
• The "inner loop" will be executed one time for each iteration of the "outer loop."

Functions

• A function is a block of code which only runs when it is called.
• It is possible to pass data (parameters) into functions.

Function Creation

• Functions are created by using the command def.

Function Calling

• Calling a function is done with func()
• Functions can also have parameters.

Default Parameter Value

• It is possible to assign default parameters to functions.

Return Values

• Use to obtain outputs from functions.

Recursion

• A defined function can call itself.

Lambda Function

• Short, anonymous function.
• Lambda-function can take number of arguments, but an only have one expression.

File Handling (Why it is needed)

• Used for storing and retrieving data persistently.
• Allows to save data even after program termination and enables sharing with program loops.
• Common configuration,logs and databases.

File Types

• Text files contain human-readable characters where examples include .txt files.
• Binary Files store data in a binary format.
• CSV Files stores tabular data using commas.
• JSON Files stores data in a structured format with key-value pairs.

File Operating

• Opening files.
• Reading from a file.
• Writing to a file.
• Closing a file.
• Error handling.

Types of file access modes

• r: Opens the file with read-only access.
• w: Opens the file with write-only access.
• a: Opens the file in the append mode.
• r+: Opens the file for both reading and writing.

Python type of file

• Text, binary, CSV and JSON files.

Different Modes and opening a file

• r, w, a etc.

How to write and add content to a file

• write()
• file = open('thefile.txt', 'w')

Method used to close

• close()
• file.close()

This quiz assesses fundamental concepts in Python, including data types, string manipulation, and basic operations. It covers string slicing, concatenation, and understanding of complex numbers. Also discussed are Anaconda Navigator and Python script execution.