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cs 16 introduction to algorithms and data structures introduction to python 2019 introduction to python 2019 due february 14th 11 59pm overview welcome to the python lab the lab is ...

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                   CS 16                                   Introduction to Algorithms and Data Structures
                   Introduction to Python - 2019
                                   Introduction to Python - 2019
                                               Due: February 14th, 11:59pm
                   Overview
                   Welcome to the Python lab! The lab is in two parts. Both parts are due on February 14th
                   at 11:59, but we strongly recommend you complete Part 1 before working on Homework 2,
                   and complete Part 2 before working on Homework 3.
                   PART1
                   1   What is Python?
                   Asnake! A snake! A scaaary snake? Yes, but Python is also a programming language that
                   you’ll be learning this semester! Python bears some resemblance to Java, but in general
                   it is cleaner and easier to read. There are a few important differences from Java that you
                   should note:
                      First, you don’t need to declare the types of variables. Thus, you write x = 1 rather
                   than int x = 1. Variables do have types, but you don’t need to announce the type when
                   you first use a variable. In fact, you can write x = 1 and then x = "abcd" in the same
                   program; after the first assignment, x is an integer; after the second, it’s a string. (N.B. In
                   general this is a very bad idea, so avoid it!)
                      Second, the environment in which you work with Python lets you type bits of code and
                   see what happens without an intermediate compiling step. This makes experimentation
                   and testing very simple.
                      Third, a feature of Python that you will grow to love and cherish is how easy it is to
                   read. Instead of using a lot of punctuation and other symbols, which are what makes code
                   in most programming languages look daunting and scary, Python uses English keywords
                   and natural-sounding syntax. For example, this is a declaration and an if-condition in
                   Python:
                   x = 1
                   if x > 0:
                      print "x is positive"
                      print "What beautiful syntax!"
                      print "Do you love Python yet?"
                   You’ll notice that instead of using curly braces to delimit code blocks, Python uses whites-
                   pace indentation. That means that correctly nesting your code now has semantic meaning,
                   instead of just making it easier for you (and your TAs) to read. We’ll learn more about
                   syntax later, so for now, just marvel at its beauty.
                   Introduction to Python - 2019      January 31, 2019                                  1
                CS 16                              Introduction to Algorithms and Data Structures
                Introduction to Python - 2019
                   Python is similar to Java in that it also handles your memory management, meaning it
                allocates memory and has a garbage collectorf to free up that memory once it is no longer
                needed, making your life a whole lot easier. If you’re not already convinced that Python
                rules...
                2   Whyshould you learn Python?
                We’ll be using Python throughout the semester to code up some of the algorithms you’ll be
                learning. As a computer scientist you should get used to learning new languages readily,
                not only because it’s an important part of the subject, but also because it’s useful (and
                fun!). Python is especially important to learn because it is used very widely as a scripting
                language – Pixar uses it for all their tools, for instance – so knowing it could one day help
                you get a job making a movie like Toy Story 3.
                3   Writing your first program in Python
                It’s tradition when learning a new programming language that your first program is a “Hello
                World” program, so let’s start out by writing a simple one-line program that prints “Hello
                World!”
                3.1   Setting up
                Run cs0160 install pythonIntro from the command line. This will install a folder
                pythonIntro in your cs0160 directory. It should contain two files primePrinter.py and
                sectionOne.py.
                   Before we begin programming, we need to configure the editor you will use to write
                your Python code. While you are free to use any editor of your choice, we recommend
                you use Atom. If you are working from a computer in the Sunlab or MSlab, complete
                Section 3.2, which will tell you how to configure Atom universally for Python code, and
                skip over Section 3.3. If you have Atom locally on your personal computer, you can follow
                the same instructions to configure it, although some of the instructions may be a little
                different depending on how you work locally. If you are working remotely, jump right to
                section 3.3 to learn how to set up Gedit, which performs better over SSH. Either way, be
                sure to begin again at Section 3.4, where you will write your first Python program!
                3.2   Working from the Sunlab or MSlab
                Open the text editor Atom, by typing atom & in your terminal. First we will make the .py
                file you will write your program in.
                   1. Create a new file: File > New File
                Introduction to Python - 2019  January 31, 2019                            2
                CS 16                              Introduction to Algorithms and Data Structures
                Introduction to Python - 2019
                   2. Save this file, File > Save, naming it helloWorld.py. The .py is very important!!
                     Make sure the file is saved in your ~/course/cs0160/pythonIntro directory.
                   Wenowneed to configure Atom to work best with Python:
                   1. From the menu bar, select Edit > Preferences. This should open up a new tab in the
                     editor. Scroll down to the Editor Settings section. This is where you can configure
                     different preferences for your Atom. Take a look at some of the options and feel free
                     to play around with them.
                   2. Change the Tab Length to be 4 and make sure the Tab Type is set to soft.
                   3. Close this tab and you’re ready to go!
                3.3   Working romotely over SSH
                Gedit performs much better over SSH, so you should use this program to work on the lab
                if you are not on a CS department computer.
                   Type gedit & into a terminal and press Enter to open Gedit.
                   First we will make the .py file you will write your program in.
                   1. Save the current (blank) new file: File > Save as...
                   2. NamethefilehelloWorld.py. The .py is very important!! Make sure the file is saved
                     in your ~/course/cs0160/pythonIntro directory.
                   Next, we have to configure Gedit to work well with Python.
                   1. Go to Edit->Preferences
                   2. Click on the Editor tab
                   3. Ensure that Tab width is set to 4
                   4. Check the box that says Insert spaces instead of tabs
                   Close out of the preferences window. You’re all set!
                3.4   Let’s get to coding!
                From CS15, you are probably familiar with using these text editors to write Java (.java)
                code. We’ll be using them to write Python (.py) files in CS16.
                   It’s important you have configured your editor as specified above because Python uses
                whitespace indentation to delimit your code (more on this later). For the sake of conve-
                nience, we insist that you use 4 spaces to indent your code. It will make your code look
                consistent across machines and prevent inconsistencies between spaces and hard tabs.
                   Now, let’s begin! Type:
                Introduction to Python - 2019  January 31, 2019                            3
                   CS 16                                    Introduction to Algorithms and Data Structures
                   Introduction to Python - 2019
                    print ‘Hello world!’
                   and save your file. Now go back to your terminal, make sure you are in the pythonIntro
                   directory and type python helloWorld.py to run the program. It will print Hello world!
                   to your terminal.
                      Hold on, do you really have to type python yourProgramName.py every time you want
                   to run a program? (Or for the especially lazy, scroll through your commands until you find
                   the last time you typed it?) Heck no! Go back to your editor and type:
                   #! /usr/bin/python
                   at the top of your helloWorld.py file. This tells your machine to use Python to interpret
                   the file when executed. Then save the file, go back to your terminal, and type chmod +x
                   helloWorld.py to make the file an executable. (If you haven’t used chmod before, it’s a
                   terminal command used to change file permissions, in this case to make your Python file
                   executable. The +x argument adds executability for the owner of the file, you!) Now if
                   you type ./helloWorld.py into your terminal your program prints Hello world! to the
                   terminal. From now on, all of your Python files should start with #!   /usr/bin/python.
                   4    Python Syntax
                   Let’s say that instead of wanting to write a program that just prints “Hello world!” and
                   then ends, you wanted to write a program with a function that takes in a string with your
                   name as the parameter, and prints “Hello !” Following the CS16 Python coding
                   conventions, the function would look like this:
                   def say_hello(name):
                        """say_hello: string -> nothing
                        Purpose: prints a greeting of the form "Hello !"
                        Example: say_hello("Seny") -> "Hello Seny!"
                        """
                        print "Hello " + name + "!" #this is the function body
                      Whenyoudefineafunction in Python, you simply write def (which is short for define),
                   followed by the name of the function, with all words lowercase and separated by underscores,
                   then the parameters in parentheses, and lastly a colon. Note that you do not need to
                   specify the type of your parameters in Python! Next, document your function with a block
                   comment! Use triple quotes (""" to create block comments much like /* would in Java. For
                   an in-line comment, use #, instead of the // from Java. This block comment should include
                   a description of the parameters and return type, the purpose of the method, and an example
                   of the method in use. This type of block comment is called a docstring and is crucial
                   to writing readable code that is easy to understand later. There is a detailed handout on
                   coding conventions on the course website that you can read for more information on writing
                   good Python.
                   Introduction to Python - 2019       January 31, 2019                                    4
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...Cs introduction to algorithms and data structures python due february th pm overview welcome the lab is in two parts both are on at but we strongly recommend you complete part before working homework what asnake a snake scaaary yes also programming language that ll be learning this semester bears some resemblance java general it cleaner easier read there few important dierences from should note first don t need declare types of variables thus write x rather than int do have announce type when rst use variable fact can then abcd same program after assignment an integer second s string n b very bad idea so avoid environment which work with lets bits code see happens without intermediate compiling step makes experimentation testing simple third feature will grow love cherish how easy instead using lot punctuation other symbols most languages look daunting scary uses english keywords natural sounding syntax for example declaration if condition print positive beautiful yet notice curly brac...

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