CS 4010 Lab 5

CS 4010 Spring 2019

Lab 5

Find a computer and log into the OSX side using your CS login name and password.

Open Firefox and find the class web page.

Open TextWrangler - use the finder window and go to applications.
Open a new text file, called Lab5.txt, to record your work today - you will paste in some of your command lines. The header of the file should look like:

Your Name
CS 4010
Lab 5
March 27, 2019

Find the Terminal - use the finder window and go to applications and then utilities.

Introduction to Python

We are going to start out using the Python interpreter
In the terminal type Python to open then interpreter, then at the prompt type the following and enter
>>> print "hello world"

For each command you run, copy the command line and the output into your Lab6.txt file.

Create a list and a sum variable

>>> L = [2,3,4,5,6]
>>> sum = 0

Now add all of the elements in the list (you will need to hit enter to get back to the prompt after sum = sum + i)

>>> for i in L:
... sum = sum + i
...
>>> print sum

Use the built-in function len() to get the length - number of elements in the list L

>>> len(L)

Use a simple if statement to check for an element in L

>>> if 3 in L:
... print 'found it'
...

Now try out the arithmetic operators to do some computations and make some notes about what you observe

>>> 16*2+5/4
>>> (16*2+5)/4
>>> (16*2+5)/4.0
>>> 3**2
>>> pow(3,2)
>>> 3%2
>>> 5%4
>>> 6%4
>>> sqrt(2)
>>> import math
>>> print "math.sqrt(100) : ", math.sqrt(100)

Now work through the examples starting on page 128 in the interpreter (not as a script yet).

You can exit the interpreter by typing ^d (control d).

Creating a Dictionary
We will start by writing the molecular weight program on page 156.
The first step is to create the dictionary of molecular weights:

find the file aminoacid_table.html in the books examples using Finder
drag the file to Firefox
once it is open, use Command-u to get the source code
copy the source code you will need to create the dictionary into TextWrangler
now write a regular expression to capture the letter and weight data (see bottom of page 156)
turn it into a dictionary be adding the name = { at the beginning and } at the end

Once you have the dictionary created, iterate through it with a for loop to compute the molecular weight of a given string. You might want to experiment with some strings of your own.
You can follow the example at the top of page 157.
Cut and paste your program and the results of running it into your Lab5.txt file.

Now that you have a dictionary, lets experiment with some of the functionality available for dictionaries:

Use the .get() function to retrieve the molecular weight for 'E'
Try printing the dictionary - what do you notice about the result?
Now try printing the keys and values separately
Next print the sorted key and compare to the keys you printed above
Modify the dnacalc.py program form earlier, using the code in the box in the middle of page 158

notice the percent calculation done in a single line
notice the formatted printing

Fun with Lists
Here are some things we would like to do with lists:

create a list from a string

create a list from the string "FDILSATFTYGNR"

define an empty list

MyList = []

define a list with elements in it

define a new list with the elements cat, dog, bird

define numerical lists with the range function

use the range function to define a list containing 1,2,3,4,5,6,7,8,9,10
can we use the range function to create the same list but in descending order?

parse strings into lists with .split()

figure out how to use split to turn the string "to be or not to be" into a list of words

added elements to lists with .append()

use the list you created with cat, dog, bird, append snake and rat

insert elements to a specific place in a list

create a list with 1,2,3,4,5 then inert the elements 9,8,7 in between 2 and 3

delete elements for a list with del

delete elements 7 and 3 from the list above using indexes and del

delete indexed elements in a list with assignment to []

delete elements 7 and 3 from the list above using assignment

use the .join() function to create a string from a list

you create a list of your choice and then turn it into a string

Again, cut and paste you command lines and output, and any programs you write into Lab5.txt

Turn it in:
Go to the CS Homework Submission System: https://www.cs.csustan.edu/cshomework/
Choose: instructor Martin
            Spring 2019
            CS4010
              Lab5
Upload the your Lab5.txt file as prompted.