Python basic
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The document provides an overview of Python programming, explaining how it directly interprets source code and covers essential concepts like variables, assignment statements, input/output, loops, and file handling. It illustrates these concepts with examples, highlighting the use of classes and objects in Python. Overall, it serves as a foundational introduction to basic programming techniques in Python.
Python basic
- 1. Python -Mayur S. Mohite
- 2. Many languages require you to compile (translate) your program into a form that the machine understands. compile execute source code byte code output Hello.java Hello.class Python is instead directly interpreted into machine instructions. interpret source code output Hello.py
- 3. Storing Values Variable : A named piece of memory that can store a value. Usage : Compute an expression's result, store that result into a variable and use that variable later in the program. Assignment statement : Stores a value into a variable. Syntax : var_name = value Examples : x=5 A variable that has been given a value can be used in expressions. Eg. x + 4 is 9
- 4. Printing Values Print : Produces text output on the console. Syntax : print "Message" print Expression Prints the given text message or expression value on the console, and moves the cursor down to the next line. Examples : print "Hello, world!" age = 45 print "You have", 65 - age, "years until retirement" Output : Hello, world! You have 20 years until retirement
- 5. Input input : Reads a number from user input. raw_input : Reads a string of text from user input. Example : age = input("How old are you? ") print "Your age is", age Output: How old are you? 53 Your age is 53 name = raw_input("Howdy, pardner. What's yer name?") print name, "... what a silly name!" Output: Howdy, pardner. What's yer name? Paris Hilton Paris Hilton ... what a silly name!
- 6. Loops for loop : Repeats a set of statements over a group of values. Example: for x in range(1, 6): print x, "squared is", x * x if statement : Executes a group of statements only if a certain condition is true. Otherwise, the statements are skipped. Example: if gpa > 2.0: print "Your application is accepted."
- 7. if/else statement : Executes one block of statements if a certain condition is True, and a second block of statements if it is False. Example: if gpa > 2.0: print "Welcome to Mars University!" else: print "Your application is denied." while loop : Executes a group of statements as long as a condition is True. good for indefinite loops (repeat an unknown number of times) Example: number = 1 while number < 200: print number, number = number * 2
- 8. String String : A sequence of text characters in a program. Strings start and end with quotation mark " or apostrophe ' characters. Examples: "hello" "This is a string" "This, too, is a string. It can be very long!" A string may not span across multiple lines or contain a " character. "This is not a legal String." "This is not a "legal" String either."
- 9. File Handling Many programs handle data, which often comes from files. Reading the entire contents of a file: variableName = open("filename").read() Example: file_text = open("bankaccount.txt").read() Reading a file line-by-line: for line in open("filename").readlines(): statements Example: count = 0 for line in open("bankaccount.txt").readlines(): count = count + 1 print "The file contains", count, "lines."
- 10. Classes And Objects A class acts like a container for all the methods and variable A class definition looks like this: class Point: pass Creating a new instance is called instantiation. To instantiate a Point object, we call a function named Point: blank = Point() We can add new data to an instance using dot notation: >>> blank.x = 3.0 >>> blank.y = 4.0