PYTHON PROGRAMMING

PYTHON PROGRAMMING

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  P.INDURANI ASSISTANT PROFESSOR &HEAD DEPARTMENT OF COMPUTER SCIENCE PARVATHY’S ARTS AND SCIENCE COLLEGE DINDIGUL 11 PYTHON PROGRAMMING
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  UNIT I Introduction –Interactive programming language. IDLE – Integrated Development and Learning Environment. • >>> - To indicate waiting for a user command. • To be printed text is enclosed between apostrophe marks. eg: >>> print(‘ Hello World’) 2
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  Example 3
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  Operators Precedence of arithmeticoperators • () Parentheses • ** Exponentiation • - Negation • / division // integer division * multiplication % modulus • + addition – subtraction 4
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  Error Message >>> 10+4(3+3) Traceback(most recent call last): File "<pyshell#10>", line 1, in <module> 10+4(3+3) TypeError: 'int' object is not callable >>> 10/0 Traceback (most recent call last): File "<pyshell#11>", line 1, in <module> 10/0 ZeroDivisionError: integer division or modulo by zero >>> 5
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  Python String Enclosed withinsingle, double or triple quotes. 6
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  Relational Operators • Tocomparing expression values. • Yield values: true, false • ASCII values are used for string comparison • Does not allow string values to be compared with numeric values. Operators are: ==, <, >, <=, >=, != 7
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  Operators Logical Operators • Combiningexpressions • Yield values: true, false • Involving arithmetic, relational and logical operators. • Evaluation using precedence rules. – Logical: not, and, or – Operators: arithmetic, relational, logical Bitwise Operators – Operate bit by bit 8
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  Variables and Assignment Statements •Variables are often called names. • Binds a variable to an object • Syntax: variable = expression Rules: • Must begin with letter or _ underscore • Contain any number of letters, digits or underscore. • Python is case sensitive • More than one variable may refer to the same object. • Shorthand Notation: >> a=a+5 9
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  Statements Keywords • Have specialmeaning. • Cannot be used for naming objects. • Eg: continue, for, while, del, true, def, except, if, return, and, else, nonlocal, etc., Script Mode • Instruction are written in a file. • Should have extension .py or .pyw 10
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  Example 11
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  Functions To solve aproblem divide it into simpler sub programs. Built-In Functions • Input – To get user input. • Eval – evaluating a string • Composition – Inner function serves as input argument to outer function. • Print – printing multiple values in a single call • Type – determining data type • Round – rounding to nearest values • Min and max – Operands must be compatible for comparison • Pow – Computing power • Math – import a module before using it. 12
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  Function Definition andcall • Comments enhance readability of the code • Single line comments start with # • Syntax: def function_name(list_of_parameters): Eg: def add(a): • Run - Click run module • Invoking the function main in the script Eg: if_name_==‘_main_’: main() • The definition of function main • An if statement 13
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  Example 14
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  • for loop:Repeats a set of statements over a group of values. – Syntax: for variableName in groupOfValues: statements • We indent the statements to be repeated with tabs or spaces. • variableName gives a name to each value, so you can refer to it in the statements. • groupOfValues can be a range of integers, specified with the range function. Eg: for x in range(1, 6): print x, "squared is", x * x Output: 1 squared is 1 2 squared is 4 3 squared is 9 4 squared is 16 5 squared is 25 Control Structures 15
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  The range functionspecifies a range of integers: • range(start, stop) - the integers between start (inclusive) and stop (exclusive) – It can also accept a third value specifying the change between values. • range(start, stop, step) - the integers between start (inclusive) and stop (exclusive) by step – Example: for x in range(5, 0, -1): print x print "Blastoff!" Output: 5 4 3 2 1 Blastoff! 16 For loop
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  • Some loopsincrementally compute a value that is initialized outside the loop. This is sometimes called a cumulative sum. sum = 0 for i in range(1, 11): sum = sum + (i * i) print "sum of first 10 squares is", sum Output: sum of first 10 squares is 385 17 Cumulative loop
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  • if statement:Executes a group of statements only if a certain condition is true. Otherwise, the statements are skipped. – Syntax: if condition: statements • Example: gpa = 3.4 if gpa > 2.0: print "Your application is accepted." 18 If statement
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  • if/else statement:Executes one block of statements if a certain condition is True, and a second block of statements if it is False. – Syntax: if condition: statements else: statements • Example: gpa = 1.4 if gpa > 2.0: print "Welcome to Mars University!" else: print "Your application is denied." • Multiple conditions can be chained with elif ("else if"): if condition: statements elif condition: statements else: statements 19 If…else… statement
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  • while loop:Executes a group of statements as long as a condition is True. – good for indefinite loops (repeat an unknown number of times) • Syntax: while condition: statements • Example: number = 1 while number < 200: print number, number = number * 2 – Output: 1 2 4 8 16 32 64 128 20 While