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Introduction to Python

Learning Objectives

  • intepreter
  • variable names
  • special variables (True, False, None, NotImplemented)
  • magic numbers
  • string indexing
  • modules (e.g. import math)

Textbook

Chapter 2, pgs 39-65

Activities

  1. install python

    • why Anaconda?
    • run the Anaconda installation script: ~wilsonp/Anaconda3-5.1.0-Linux-x86_64.sh
    • select the default location, it should be $HOME/anaconda3

  2. Project Planning - revisited

    • stages of development
      • identify milestones that incrementally increase the scope and complexity
      • e.g. if the ultimate problem is a non-linear 3-D problem, consider starting with a 1-D linear approximation and gradually adding dimensionality and the non-linear components
      • this allows reaching "working" versions at each milestone and possibly easier testing

  3. start ipython

    • standard python REPL
    • the iPython environment
    • Jupyter notebooks
    • two windows with editor

  4. comments

    • hashtag anywhere in line
    • start with liberal use of comments
    • good choices of variable names and data structure can reduce need for comments
    • document why and not what

  5. variable names

    • variable assignment
    • types
    • choosing variable names
    • special variables
    • operators
    • strings
      • inndexing: zero
      • slicing: start:end:step, negative indices, empty entries
      • string math: concat, multiply
      • builtin functions - len(), upper, isdigit, strip, format

  6. magic "numbers"

    • any quantity that has semantic meaning should be assigned to a variable that expresses that meaning
      1. provides meaning
      2. frequently used in multiple places and allows single change for consistency

  7. importing modules

    • functionality available in modular units
    • import math
      • try cos() first
    • different imports:
      • import math -> math.cos()
      • from math import cos() -> cos()
        • from math import *
      • import math as m -> m.cos()
    • important modules: os, sys, math, argparse
      • finding help