Due Wednesday,October 16
Basic Scripting in Python
In this lab, you will be learning the basics of scripting in python,
to help you learn how to automate part of your workflow for doing
- Log on to one of the computers in the lab.
- Open up a terminal to the lab7 directory
- Make the scripts in this directory
- When you are done, submit all of the .class files. In order to
submit your file, you will need to be SSH'd in to agate.
~cs520/bin/DoSubmission.py lab7 script1.py script2.py ... etc
Please submit whatever you have at the end of lab, even if it is
incomplete. You have the rest of today to finish this assignment.
Basic Tasks in Python
A few important things to know
Python is a dynamically typed language, meaning you don't declare the
type of whatever you are using. In fact, you don't have to declare a
variable at all, you just need to say x = whatever and x takes the
value of whatever. Variables have types at runtime, and if you try to
do something invalid with a variable (like add to a string or write to
an int) you just get a runtime error.
Probably the strangest thing about python is that whitespace and
indentation matter a whole lot. While C, Java, C++, and a number of
other languages get their loop and if levels from curly brackets,
python divines this information from the indentation of the file.
Printing stuff in python is incredibly simple, it is quite literally
print x. If you are having trouble figuring out what something is, it
often helps to print it to see what you are dealing with. MAKE SURE
YOU COMMENT OUT DEBUGGING PRINT STATEMENTS WHEN YOU ARE DONE. If I
find any uncommented out debugging print statements I will deduct
Basic Hello World
Make a python program called "hello.py" that prints out "hello
world". There are a number of basic tutorial sites online, this
is a fairly concise tutorial that tells you how to do that step by step.
Writing to a file
Make a python program called "hello_write.py" that writes "hello
world" into a file called "hello_python".
has the information you need to know how to do this, but it also
contains a bunch of stuff that isn't particularly relevant to this
Calling a subprocess
Make python program called lsfile.py that runs the command "ls" with
the "-al" option on the directory "~/" and writes the output to a file
called "lspython". In order to do this, you will need to remember how
to write something to a file.
has some useful information about how to get the subprocess module
Basic String operations
Make a string in python as follows:
longstring = "1 2 7.77"
Make a python script called splitstring.py that takes that string, and
splits it into 3 numbers: x, y, and z. The python documentation
isn't the greatest in my opinion, but it does have useful information,
if you know where to look. The string type has a split method that
you can use to split the string apart into a list of strings. The
first step is to split that string into a list of 3 strings, each
containing one number. Use the website above to find the how that
command works. Once you have split the string, you should have a list
of strings. If you want to convert one type to another type, there is
a little built in function to do so. For example, if you want an int
from something, you do int(something) and python tries to convert
something into an int. The same applies to strings and floats. For
whatever reason, python won't convert numbers to strings
automatically, which is mildly annoying in my opinion, so if you have
a number n and you want to concatenate it with a string, you have to
do "mystring + str(n)" instead of "mystring + n".
For more information about lists, you can look here. That site has a
ton of stuff about how to do things with lists, but the part that is
most important is accessing lists, which you need to do to assign the
x the number representation of the first thing in the list.
Write a python script called forloop.py that prints out the word
"forloop" followed by a space, followed by a number. The program
should do this five times, printing the numbers 10 through 14.
This has some
useful information about how to do that. Remember python figures out
loop and if level based upon indentation.
Iterating over a list
Make a python script called stringloop.py that prints out every word
in a string on its own line. Make a variable which is a string as
whatever = "Python is my favorite thing ever"
Next, turn whatever into a list of the individual words in the string
(delimited by space). On the previously mentioned website, there is a
section called "lists as an iterable" which shows how this can be done.
I will be grading your programs primarily on how well they work, but I
will also be considering how the code looks. These programs are
extremely simple and should be quite small; if you find yourself
writing more than a few lines of code, you are probably doing
something wrong, and I would recommend you speak to me.
- 20 points will be awarded for hello.py
- 20 points will be awarded for hello_write.py
- 20 points will be awarded for lsfile.py
- 20 points will be awarded for splitstring.py
- 10 points will be awarded for forloop.py
- 10 points will be awarded for stringloop.py