CompSciWeek3

Reading Assignment

• Beginning Python, Chapter 6
• Algorithms, Chapters 1-2
  • focus on tree data structures (formal complexity next week)
  • ignore python 'Class' for now

Class 1: Intermediate shell utilities

• commands
  • man/info <-> help()
  • ls <-> dir()
  • cat <-> print
  • grep <-> string.find()
  • sort <-> list.sort()
  • head / tail <-> list.__slice__ (i.e. l[:10])
  • tr, sed <-> string.replace()
  • find
  • w, top, last
• shell variables
• control flow
  • shell functions -- f() { commands; }
  • pipes, redirection, &&, || -- a | b, a && b, a || b
  • for, while loops -- for i in 1 2 3; do ... done, for((i=0; i<$n; i++)); do ... done

References:

• Python Syntax
• Bash Syntax
• Sed One-Liners

Class 2: Python vs. shell

• Reading / Writing Files
• Advanced control structures (list comprehensions)
• Code profiling
• Hash tables
• Graphs

Homework 2 - due Tuesday, Sept. 16

Since the due date was pushed back, re-submitted homework will be accepted in place of the original. As a reminder, all homework must be done on your own. Send the homework as a single txt file attachment with the subject line "Sci Comp HW2". If you send a pdf, format it using the script Code:text2pdf.

• Coding problems:
  • Write a loop to sum 100 random numbers (import random, random.random()) using each of the following control structures: for, while, list and `tuple` comprehension. The first two can generate numbers in the loop, the last two must create iterators / generators and can use the python builtin `sum' function.
  • Write a shell loop to save 100 numbers from $RANDOM to a file, writing one number per line. (hint: use the shell append re-direction, >> instead of the usual re-direction >)
  • Write a shell loop to sum files with 1 number per line. -- use shell math expressions, like a=$(($a*12))
  • Write python and shell programs to print the smallest 10 numbers from such a file.
  • Write a text processing script using sed to get the numbers for the following quantities from File:Multiwfn.txt
    1. Basin electric monopole moment: (1 number for ea. line)
    2. Basin electric dipole moment: and Basin electron contribution to molecular dipole moment: (3 numbers from ea. line) The input is tagged X=, etc, the output should have only numbers.
    • (Clarification) The output (if run) would be one file with all the "monopole" numbers, 1 per line, another with all the "dipole" numbers, 3 per line. I just want the code, not the output.