PyQuick Basic Python Class: Day 1

Introduction

• Instructor: Nick Parlante
• Affiliations: Google engEDU group (technical training), Stanford lecturer
• Class Duration: 2 days, covering basic, useful Python
• Prerequisites:
  • Some experience with any programming language
  • Basic understanding of programming concepts like variables

Class Format

• Structure: Mix of lectures and coding sections
• Materials: Written materials available on PyQuick page [link provided in the class]
• Focus: Introduction to strings, lists, modules, etc.
• Approach:
  • Lectures to cover basic ideas
  • Coding sections to practice hands-on learning

Overview of Python

• History: Created by Guido van Rossum in 1990
• Popularity: Recently gained momentum due to its easy and intuitive design
• Category: Scripting Language
  • Similar to Perl, Bash, Ruby, JavaScript
  • No heavy type system
• Interactive Nature: Python supports quick experimentation using interactive mode
• Usages
  • Suitable for small tasks and scripts
  • Debate on its efficacy in large-scale projects

The Python Interpreter

• Interactive Mode: Type python to start, can execute single lines of code
• Quick turnaround: Ideal for testing small snippets
• Commands Example:
  • Variable assignment: a = 6
  • Print value: print(a)
  • Dynamic typing: a = 'hello', print(a)

Basic Syntax

• Functions: Defined using def keyword
  • Example: def main(): print('Hello')
• Imports: Bringing in external modules using import keyword
  • Example: import sys, print(sys.argv)
• Command-line arguments: Accessed via sys.argv
  • First element is the script name
• Running Scripts:
  • python hello.py
  • ./hello.py (with execute permissions)

Python's Design Philosophy

• Dynamic Typing: No need to declare type of variables
• Indentation: Used for block delimitation instead of { }
  • Default: 2 spaces (Google standard)
  • Example function:

    def hello(name):
        print('Hello', name)
    

• Error Handling:
  • Immediate feedback on errors
  • Encourages good testing practices
• Comparisons: Deep, intuitive comparisons using ==
  • Example: if name == 'Alice': print('Hi Alice')
  • Logical operators: and, or, not

Strings

• Declaration: Single or double quotes
  • Example: 'hello', "world"
• Immutability: Strings cannot be changed once created
• Common Methods:
  • Length: len(string)
  • Lowercase: string.lower()
  • Find: string.find('sub')
• String Formatting:
  • Concatenation: a + b
  • Format string: "%s %d" % ('hello', 42)
• Unicode: Handles Unicode, minor differences in creation
• Indexing & Slicing:
  • Indexing: string[index]
  • Slicing: string[start:end]
    • Example: a[1:4] gets substring from index 1 to 3
    • Omitting start or end: a[1:], a[:3]
    • Negative indexing: From the end of the string a[-3:]

Modules & Documentation

• Common Modules: sys, os, etc.
  • Importing: import module_name
  • Using Functions: module.function()
• Documentation:
  • Use dir() and help() functions
  • Google search for quick answers

Exercises

• Location: PyQuick page, day1/ directory
• Exercise File: string1.py (basic string operations)
  • Write code to complete tasks, test with provided test cases
  • Optional additional exercises in string2.py
• Time Allocation: Work on exercises for ~30 minutes, then break for lunch

Tips

• Indentation: Use spaces, not tabs (use -tt flag to avoid mixing)
• Exploration: Utilize interpreter for quick experiments

Conclusion

• End of Lecture: Proceed to exercises and practical coding
• Next Session: Continue after lunch and move to more exercises and advanced topics