Week 1, Problem 1: Data!
[25
points; individual or pair]
Part
0: Logging in and running Python and IDLE
An easy way to start Python and IDLE is by clicking on
the IDLE icon in the "dock" at the bottom of the screen. It's the one
with the stylized yellow and blue pythons on it. If you can’t find it, click
the Windows start button shown below:
and click on IDLE
for Python. After that, open a new file and add a suitable comment at the
top—for example:
# Homework 1, Problem 1 (Lab)
# 04/07/2012
Save your file as hw1pr1.py
- perhaps
on the desktop (easy to find) or in a new folder (better organized).
Part
1: working at the Python interpreter (or shell)
Arithmetic with numbers, lists, strings, and
booleans.
To get started, try a few arithmetic, string, and list
expressions in the Python interpreter, e.g.,
>>>
40 + 2
42
>>> 40 ** 2
1600
>>> 40 % 2
0
>>> 'hi
there!'
hi there! (notice
Python's politeness!)
>>> 'who
are you?'
who are you? (though
sometimes it's a bit touchy.)
>>> L =
[0,1,2,3]
You
can label data (here, a list) with a name (here, the name L)
(no response from
Python)
>>> L
[0,1,2,3] You
can see the data (here, a list) referred to by a name (here, L)
>>> L[1:]
[1,2,3] You
can slice lists (here, using the name L)
>>> L[::-1]
[3,2,1,0] You
can reverse lists (or strings!) using "skip"-slicing with a -1 as the amount to skip.
>>>
[0,1,2,3][1:]
[1,2,3] You
can slice lists using the raw list instead of the name (Not that this would be
very useful, admittedly!)
>>> 100*L +
[42]*100
(a list with 500
elements that I'm too lazy to type here)
>>> L = 42 You
can reassign the name L to
another value, even of a different type- now, L names the integer 42, instead of the
list it used to represent.
(no response from
Python)
>>> L == 42 Two
equals are different than 1! This tests for equality.
True
>>>
L != 42
This
tests for "not equal."
False
Errors or Exceptions
If you didn't type things in perfectly, Python will reply
with an error or an exception, as it is often called. See if you can
make Python create the following exceptions, but don't spend more than a minute
or so in total!
SyntaxError
TypeError (try
slicing an integer for example!)
ZeroDivisionError
IndexError (try
an out-of-bounds index)
OverflowError (remember
that integers will crash the machine before overflowing)
Part
2: Lists of integers
This problem will exercise your slicing-and-indexing skills.
First, you should copy (or type) into your
hw1pr1.py file the following lines:
# starting lists for part 2
pi = [3,1,4,1,5,9]
e = [2,1,7]
When you hit F5 (or click Run and then click Run Module F5), these two lists
will be recognized by the Python shell.
The challenge is to create several lists using only
the list labeled pi, the list labeled e,
and the four list operations here --
list indexing pi[0]
list slicing e[1:]
list concatenation, + pi[:1]
+ e[1:]
(don't use + to
add values numerically)
the list-making operator, [ , ] [
e[2], e[0] ]
For each one, place your answer into an appropriate
variable in your hw1pr1.py file
(see example below). Include a comment on the line above, as well. Though not
mandatory, you might try to use as few operations as possible, to keep your
answers elegant and efficient. For example,
Example
problem Use pi and/or e to
create the list [2,5,9]. Store
this list in the variable answer0.
Answer
to the example problem
# Creating the list [2,5,9]
answer0 = [e[0]] + pi[-2:]
Please leave a blank line or two between your answers (to
keep the graders happy)!
Remember that you can use the python interpreter to try things out!
Here
are the problems:
Use pi and/or e to
create the list [7,1]. Store this list in the variable answer1.
Use pi and/or e to
create the list [9,1,1]. Store this list in the
variable
answer2.
Use pi and/or e to
create the list [1,9,5,1,4]. Store this list in the
variable
answer3.
Use pi and/or e to
create the list [1,2,3,4,5,5,4,3,2,1]. Store this list in the
variable answer4.
Part 3: Strings
This
problem continues in the style of the last one, but uses strings rather than
lists. So, it asks you to create specified strings that result from using only
the following three string literals, which you should
type into your hw1pr1.py file at this point:
n = 'northwestern'
u = 'university'
c = 'class_eecs_110_python'
You
may use any combination of these four string operations:
String
indexing, e.g., n[0]
String
slicing, e.g., u[1:]
String
concatenation, +,
e.g., c + n
Repetition,
*, e.g., 42*c (using integers is OK
here)
Again,
less is more: the number of operations in our shortest answers are in parentheses- you might find even more
efficient ones! However, any answer is OK - there's no requirement to use fewer operations.
Example problem: Use n and c to create 'nano'. Store this string in the variable answer42.
Answer to example
# Creating the string 'nano'
answer42 = n[0] + c[2] + n[0] + c[-2]
Create
northeasternuniversity Store this string in the variable answer5.
Create
east_river Store this string in the variable answer6.
Create nirvana Store this string in the variable answer7.
Create easterparty_110110 Store this string in the variable answer8.
Create we_have_clinteast_in_eecs110 Store this string in the variable answer9.
If
you have gotten to this point, you have completed the first problem from Lab 1! You should submit your hw1pr1.py file at the Canvas.
Next