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Introduction to Python

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Mohammed Sikander

This document provides an introduction to the Python programming language. It discusses Python's design philosophy emphasizing readability. It also covers printing messages, reading input, variables and data types, operators, and basic syntax like comments and identifiers. Arithmetic, relational, logical and bitwise operators are explained along with examples.

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Introduction to Python Programming
Python Printing Messages on Screen Reading input from console Python Identifiers and Keywords Data types in Python Operators Using math library function
 Developed by GuidoVan Roussum in 1991.  Python is processed at runtime by the interpreter.  There is no need to compile your program before executing it.  Python has a design philosophy that emphasizes code readability.
Hello World Program mohammed.sikander@cranessoftware.com 4 >>> print(‘Hello’) >>> print(‘Welcome to Python Programming!')
Print Statement #Python 2.x Code #Python 3.x Code print "SIKANDER" print 5 print 2 + 4 SIKANDER 5 6 The "print" directive prints contents to console.  In Python 2, the "print" statement is not a function,and therefore it is invoked without parentheses.  In Python 3, it is a function, and must be invoked with parentheses. (It includes a newline, unlike in C)  A hash sign (#) that is not inside a string literal begins a comment. All characters after the # and up to the end of the physical line are part of the comment and the Python interpreter ignores them. print("SIKANDER") print(5) print(2 + 4) Output
Python Identifiers  Identifier is the name given to entities like class, functions, variables etc.  Rules for writing identifiers  Identifiers can be a combination of letters in lowercase (a to z) or uppercase (A to Z) or digits (0 to 9) or an underscore (_).  An identifier cannot start with a digit.  Keywords cannot be used as identifiers.  We cannot use special symbols like !, @, #, $, % etc. in our identifier.
Python Keywords  Keywords are the reserved words in Python.  We cannot use a keyword as variable name, function name or any other identifier.  They are used to define the syntax and structure of the Python language.  keywords are case sensitive.  There are 33 keywords in Python 3.3.
Keywords in Python programming language False class finally is return None continue for lambda try True def from nonlocal while and del global not with as elif if or yield assert else import pass break except in raise All the keywords except True, False and None are in lowercase
PythonVariables  A variable is a location in memory used to store some data (value).  They are given unique names to differentiate between different memory locations.The rules for writing a variable name is same as the rules for writing identifiers in Python.  We don't need to declare a variable before using it.  In Python, we simply assign a value to a variable and it will exist.  We don't even have to declare the type of the variable.This is handled internally according to the type of value we assign to the variable.
Variable assignment  We use the assignment operator (=) to assign values to a variable.  Any type of value can be assigned to any valid variable.
Multiple assignments  In Python, multiple assignments can be made in a single statement as follows: If we want to assign the same value to multiple variables at once, we can do this as x = y = z = "same"
Data types in Python  Every value in Python has a datatype.  Since everything is an object in Python  Data types are actually classes and variables are instance (object) of these classes.  Numbers  int  float  String – str  Boolean - bool
Type of object – type()  type() function can be used to know to which class a variable or a value belongs to.
Reading Input Python 2.x Python 3.x  print("Enter the name :")  name = raw_input()  print(name)  print("Enter the name :")  name = input()  print(name) If you want to prompt the user for input, you can use raw_input in Python 2.X, and just input in Python 3.
 name = input("Enter the name :")  print(“Welcome “ + name)  Input function can print a prompt and read the input.
Arithmetic Operators Operator Meaning Example + Add two operands or unary plus x + y +2 - Subtract right operand from the left or unary minus x - y -2 * Multiply two operands x * y / Divide left operand by the right one (always results into float) x / y % Modulus - remainder of the division of left operand by the right x % y (remainder of x/y) // Floor division - division that results into whole number adjusted to the left in the number line x // y ** Exponent - left operand raised to the power of right x**y (x to the power y)
Arithmetic Operators
What is the output
 Data read from input is in the form of string.  To convert to integer, we need to typecast.  Syntax : datatype(object)
Introduction to Python
Exercise  Write a program to calculate the area of Circle given its radius.  area = πr2
Introduction to Python
Introduction to Python
 Write a program to calculate the area of circle given its 3 sides.  s = (a+b+c)/2  area = √(s(s-a)*(s-b)*(s-c))
Introduction to Python
Given the meal price (base cost of a meal), tip percent (the percentage of the meal price being added as tip), and tax percent (the percentage of the meal price being added as tax) for a meal, find and print the meal's total cost. Input 12.00 20 8 Output The total meal cost is 15 dollars.
Introduction to Python
 Temperature Conversion.  Given the temperature in Celsius, convert it to Fahrenheit.  Given the temperature in Fahrenheit, convert it to Celsius.
Relational operators  Relational operators are used to compare values.  It returns True or False according to condition Operator Meaning Example > Greater that - True if left operand is greater than the right x > y < Less that - True if left operand is less than the right x < y == Equal to - True if both operands are equal x == y != Not equal to - True if operands are not equal x != y >= Greater than or equal to - True if left operand is greater than or equal to the right x >= y <= Less than or equal to - True if left operand is less than or equal to the right x <= y
Introduction to Python
Introduction to Python
Logical operators Operator Meaning Example and True if both the operands are true x and y or True if either of the operands is true x or y not True if operand is false (complements the operand) not x
Introduction to Python
Bitwise operators  Bitwise operators operates on individual bits of number. Operator Meaning Example & Bitwise AND 10 & 4 = 0 | Bitwise OR 10 | 4 = 14 ~ Bitwise NOT ~10 = -11 ^ Bitwise XOR 10 ^ 4 = 14 >> Bitwise right shift 10>> 2 = 2 << Bitwise left shift 10<< 2 = 42
Compound Assignment operators Operator Example Equivatent to = x = 5 x = 5 += x += 5 x = x + 5 -= x -= 5 x = x - 5 *= x *= 5 x = x * 5 /= x /= 5 x = x / 5 %= x %= 5 x = x % 5 //= x //= 5 x = x // 5 **= x **= 5 x = x ** 5 &= x &= 5 x = x & 5 |= x |= 5 x = x | 5 ^= x ^= 5 x = x ^ 5 >>= x >>= 5 x = x >> 5 <<= x <<= 5 x = x << 5
Precedence of Python Operators Operators Meaning () Parentheses ** Exponent +x, -x, ~x Unary plus, Unary minus, Bitwise NOT *, /, //, % Multiplication,Division, Floor division, Modulus +, - Addition,Subtraction <<, >> Bitwise shift operators & Bitwise AND ^ Bitwise XOR | Bitwise OR ==, !=, >, >=, <, <=, is, is not, in, not in Comparisions,Identity, Membership operators not Logical NOT and Logical AND or Logical OR

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Introduction to Python

  • 2. Python Printing Messages on Screen Reading input from console Python Identifiers and Keywords Data types in Python Operators Using math library function
  • 3.  Developed by GuidoVan Roussum in 1991.  Python is processed at runtime by the interpreter.  There is no need to compile your program before executing it.  Python has a design philosophy that emphasizes code readability.
  • 4. Hello World Program mohammed.sikander@cranessoftware.com 4 >>> print(‘Hello’) >>> print(‘Welcome to Python Programming!')
  • 5. Print Statement #Python 2.x Code #Python 3.x Code print "SIKANDER" print 5 print 2 + 4 SIKANDER 5 6 The "print" directive prints contents to console.  In Python 2, the "print" statement is not a function,and therefore it is invoked without parentheses.  In Python 3, it is a function, and must be invoked with parentheses. (It includes a newline, unlike in C)  A hash sign (#) that is not inside a string literal begins a comment. All characters after the # and up to the end of the physical line are part of the comment and the Python interpreter ignores them. print("SIKANDER") print(5) print(2 + 4) Output
  • 6. Python Identifiers  Identifier is the name given to entities like class, functions, variables etc.  Rules for writing identifiers  Identifiers can be a combination of letters in lowercase (a to z) or uppercase (A to Z) or digits (0 to 9) or an underscore (_).  An identifier cannot start with a digit.  Keywords cannot be used as identifiers.  We cannot use special symbols like !, @, #, $, % etc. in our identifier.
  • 7. Python Keywords  Keywords are the reserved words in Python.  We cannot use a keyword as variable name, function name or any other identifier.  They are used to define the syntax and structure of the Python language.  keywords are case sensitive.  There are 33 keywords in Python 3.3.
  • 8. Keywords in Python programming language False class finally is return None continue for lambda try True def from nonlocal while and del global not with as elif if or yield assert else import pass break except in raise All the keywords except True, False and None are in lowercase
  • 9. PythonVariables  A variable is a location in memory used to store some data (value).  They are given unique names to differentiate between different memory locations.The rules for writing a variable name is same as the rules for writing identifiers in Python.  We don't need to declare a variable before using it.  In Python, we simply assign a value to a variable and it will exist.  We don't even have to declare the type of the variable.This is handled internally according to the type of value we assign to the variable.
  • 10. Variable assignment  We use the assignment operator (=) to assign values to a variable.  Any type of value can be assigned to any valid variable.
  • 11. Multiple assignments  In Python, multiple assignments can be made in a single statement as follows: If we want to assign the same value to multiple variables at once, we can do this as x = y = z = "same"
  • 12. Data types in Python  Every value in Python has a datatype.  Since everything is an object in Python  Data types are actually classes and variables are instance (object) of these classes.  Numbers  int  float  String – str  Boolean - bool
  • 13. Type of object – type()  type() function can be used to know to which class a variable or a value belongs to.
  • 14. Reading Input Python 2.x Python 3.x  print("Enter the name :")  name = raw_input()  print(name)  print("Enter the name :")  name = input()  print(name) If you want to prompt the user for input, you can use raw_input in Python 2.X, and just input in Python 3.
  • 15.  name = input("Enter the name :")  print(“Welcome “ + name)  Input function can print a prompt and read the input.
  • 16. Arithmetic Operators Operator Meaning Example + Add two operands or unary plus x + y +2 - Subtract right operand from the left or unary minus x - y -2 * Multiply two operands x * y / Divide left operand by the right one (always results into float) x / y % Modulus - remainder of the division of left operand by the right x % y (remainder of x/y) // Floor division - division that results into whole number adjusted to the left in the number line x // y ** Exponent - left operand raised to the power of right x**y (x to the power y)
  • 18. What is the output
  • 19.  Data read from input is in the form of string.  To convert to integer, we need to typecast.  Syntax : datatype(object)
  • 21. Exercise  Write a program to calculate the area of Circle given its radius.  area = πr2
  • 24.  Write a program to calculate the area of circle given its 3 sides.  s = (a+b+c)/2  area = √(s(s-a)*(s-b)*(s-c))
  • 26. Given the meal price (base cost of a meal), tip percent (the percentage of the meal price being added as tip), and tax percent (the percentage of the meal price being added as tax) for a meal, find and print the meal's total cost. Input 12.00 20 8 Output The total meal cost is 15 dollars.
  • 28.  Temperature Conversion.  Given the temperature in Celsius, convert it to Fahrenheit.  Given the temperature in Fahrenheit, convert it to Celsius.
  • 29. Relational operators  Relational operators are used to compare values.  It returns True or False according to condition Operator Meaning Example > Greater that - True if left operand is greater than the right x > y < Less that - True if left operand is less than the right x < y == Equal to - True if both operands are equal x == y != Not equal to - True if operands are not equal x != y >= Greater than or equal to - True if left operand is greater than or equal to the right x >= y <= Less than or equal to - True if left operand is less than or equal to the right x <= y
  • 32. Logical operators Operator Meaning Example and True if both the operands are true x and y or True if either of the operands is true x or y not True if operand is false (complements the operand) not x
  • 34. Bitwise operators  Bitwise operators operates on individual bits of number. Operator Meaning Example & Bitwise AND 10 & 4 = 0 | Bitwise OR 10 | 4 = 14 ~ Bitwise NOT ~10 = -11 ^ Bitwise XOR 10 ^ 4 = 14 >> Bitwise right shift 10>> 2 = 2 << Bitwise left shift 10<< 2 = 42
  • 35. Compound Assignment operators Operator Example Equivatent to = x = 5 x = 5 += x += 5 x = x + 5 -= x -= 5 x = x - 5 *= x *= 5 x = x * 5 /= x /= 5 x = x / 5 %= x %= 5 x = x % 5 //= x //= 5 x = x // 5 **= x **= 5 x = x ** 5 &= x &= 5 x = x & 5 |= x |= 5 x = x | 5 ^= x ^= 5 x = x ^ 5 >>= x >>= 5 x = x >> 5 <<= x <<= 5 x = x << 5
  • 36. Precedence of Python Operators Operators Meaning () Parentheses ** Exponent +x, -x, ~x Unary plus, Unary minus, Bitwise NOT *, /, //, % Multiplication,Division, Floor division, Modulus +, - Addition,Subtraction <<, >> Bitwise shift operators & Bitwise AND ^ Bitwise XOR | Bitwise OR ==, !=, >, >=, <, <=, is, is not, in, not in Comparisions,Identity, Membership operators not Logical NOT and Logical AND or Logical OR