Python

1
Python May 11

• Briefing
• Course overview
• Introduction to the language
• Lab

2
Python

• Why computer programming?
• Computer is a general-purpose machine, born to be
  programmed
• We want to solve many types of problems
• Our goals
• Become multi-lingual
• Practice with design implementation
• Learn by doing start simple
• Help available
• Textbook, python.org, tutorials

3
Background

• First released, 1991
• Guido van Rossum, CWI, Netherlands
• Dissatisfaction with existing languages
• High-level, multi-purpose language
• Relatively easy to learn use (we hope!)
• Procedural, object oriented or functional
• Interpreted
• Interface to OS, file system, Web
• Some data structures built into language
• Standard library
• (More details in sections 1.3 and 1.5)

4
Initial To-Do

• Essential skills special features of language
• Routine stuff
• Source file name ends in .py
• How to run interpreter (command line or IDE)
• Program structure
• I/O
• Interactive, file formatting
• Variables, identifiers
• Doing math
• Comments, tokens, whitespace, style conventions

5
continued

• Control structures
• Asking questions, repeating stuff
• nesting
• How to make comparisons
• Boolean operations and/or/not
• Functions/procedures parameters, returns
• Data structures
• String, dynamically-sized list, etc.
• Standard (i.e. run-time) library
• Random numbers, etc.

6
In the end

• How can you tell if youve mastered a language?
• Write a game
• Given a spec or algorithm, can you implement it?
• You may prefer to do something in Python!
• You never need to know everything. Know where to
  find stuff quickly
• This course lies between first 2 prog. courses
• Youll see more operations applications than in
  the 1st course. Not as theoretical as 2nd
  course.

7
Beginning

• Versions 2.x and 3.x
• Lab lets use IDE such as ActivePython
• Free, simple, includes debugger ?
• Code can by entered
• directly in shell (good for experimenting!)
• in a file, which we can save and reuse later

8
Initial nuts bolts

• Comments begin with , go to end of line
• Statements dont end in semicolon
• Dont arbitrarily indent code
• Put \ at end of line to continue statement
• Variables are not declared
• Interactive output
• Version 2.6 print statement print
  name
• Version 3.0 print function print
  (name)

9
continued

• Examples
• print Hello, world
• print 743
• Interactive input
• input( ) for getting a number
• raw_input( ) for getting a string
• name raw_input(What is your name)

10
Whats next?

• Lab
• Please read chapter 2
• Practice with
• Basic I/O
• Mathematical operations
• Strings
• Simple if statement
• Simple loop