{"id":2203,"date":"2016-11-28T12:48:13","date_gmt":"2016-11-28T20:48:13","guid":{"rendered":"http:\/\/miriamposner.com\/classes\/dh101f16\/?page_id=2203"},"modified":"2016-11-28T16:42:24","modified_gmt":"2016-11-29T00:42:24","slug":"lets-play-with-python","status":"publish","type":"page","link":"http:\/\/miriamposner.com\/classes\/dh101f16\/tutorials-guides\/programming\/lets-play-with-python\/","title":{"rendered":"Let’s play with Python!"},"content":{"rendered":"
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\"People<\/a>
People always feel compelled to make dumb Monty Python jokes when they hear about Python. I know you won’t do that, though.<\/figcaption><\/figure>\n

It’s really fun to work in the terminal, but Python is a more broadly useful programming language. A lot of people use it to manipulate data and documents, automate tasks, and even build complex applications.<\/p>\n<\/div>\n

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Python is installed on the Lab computers. If you want to install it on your own computer later, here are instructions<\/a> for how to do it.<\/p>\n

We’ll start by using Python in the terminal, and then we’ll move to a Python-specific coding environment called IDLE.<\/p>\n

(By the way, you may wonder why it’s called Python<\/a>.)<\/p>\n<\/div>\n

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Start Python<\/h2>\n
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This is incredibly complicated. Type<\/p>\n

python<\/code><\/p>\n

and press return<\/strong>. You should then see some information about the version of Python you’re running, followed by three little angled brackets, like this: >>> Those three angled brackets mean your computer is waiting for you to tell it what to do, in the Python computer language.<\/p>\n<\/div>\n

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\"start-python\"<\/a><\/div>\n<\/div>\n<\/div>\n
<\/div>\n
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Pretend your computer is a giant calculator<\/h2>\n
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Your computer is waiting for you to give it instructions in Python, so let’s do that. Type<\/p>\n

2+2<\/code><\/p>\n

and press return<\/strong>.<\/p>\n

Python, as you can see, recognizes integers, <\/strong>like the number 2, and operators<\/strong>, like the plus sign (as well as other operators, like the multiplication (*) and division (\/) signs). If you want, try writing some other arithmetical expressions and pressing return<\/strong> so that your computer will tell you the answer.<\/p>\n

Admire yourself as you do this. You look like a hacker!<\/p>\n

\"pretend-your-computer-is-a-giant-calculator\"<\/a><\/p>\n<\/div>\n

<\/div>\n<\/div>\n
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Concatenate strings<\/h2>\n
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In programming parlance, a string<\/strong> is a series of characters. Concatenate<\/strong> is a fun word that basically means “stick them together.” In Python, you denote a string by surrounding it with quotation marks. You concatenate with the plus sign. Try this:<\/p>\n

\"I\"+\"love\"+\"digital\"+\"humanities\"<\/code><\/p>\n

and press return<\/strong>. Your computer should spit out a concatenated version of the strings you fed it.<\/p>\n

\"concatenate-strings\"<\/a><\/p>\n<\/div>\n

<\/div>\n<\/div>\n
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Assign a variable<\/h2>\n
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You can begin unlocking the power of a programming language when you start using variables<\/strong>. A variable is a set of characters that stands for<\/em> something else. A variable could stand for a string, or a number, or even a series of operations. We’ll assign a variable to a string. Type:<\/p>\n

a = \"I love digital humanities\"<\/code><\/p>\n

and press return<\/strong>. Then type<\/p>\n

print(a)<\/code><\/p>\n

and press return. (With a lot of programming languages, print<\/strong> doesn’t mean “print something on paper”; it means “show me this on the screen.”)<\/p>\n

Your computer will show you the contents of the variable called a<\/strong> — namely, the string “I love digital humanities.”<\/p>\n

\"assign-a-variable\"<\/a><\/p>\n<\/div>\n

<\/div>\n<\/div>\n
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Perform operations with variables<\/h2>\n
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What do you think will happen if you type<\/p>\n

a+a+a+a<\/code><\/p>\n

and press return<\/strong>? Try it and see.<\/p>\n

Now try<\/p>\n

a*3<\/code><\/p>\n

and press return<\/strong>.<\/p>\n

\"perform-operations-with-variables\"<\/a><\/p>\n<\/div>\n

<\/div>\n<\/div>\n
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Open your IDLE<\/h2>\n
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As you’ve seen, you can work with Python directly in the terminal. But it’s kind of a pain, because you have to type in one line at a time, and you can’t go back and change stuff once you’ve pressed return.<\/p>\n

Most people, instead of writing programs directly in the terminal, will write code in a text document, which you can work on and save to run again whenever you want. You can use any kind of code editor to write Python — you just save the document with the file extension .py<\/strong> so that your computer knows it’s a Python program.<\/p>\n

Today, we’ll use IDLE<\/strong> to write our Python program. IDLE, which stands for Integrated DeveLopment Environment, is sort of a combination of a text editor and a terminal. You’ll write your Python code in a document and then press Run<\/strong> to make the program go.<\/p>\n

To find IDLE, go to your Applications<\/strong> folder and open up the folder called Python 3.5<\/strong>. (The version is important.) Once inside that folder, find the application called IDLE<\/strong> and double-click.<\/p>\n

\"open-your-idle\"<\/a><\/p>\n<\/div>\n

<\/div>\n<\/div>\n
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Understanding IDLE<\/h2>\n
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When IDLE first opens, you’ll see the shell<\/strong>, which is kind of like your terminal, but just running Python. You won’t do your coding there, though. Instead, open a new, blank file by going to File<\/strong>, then New<\/strong> File<\/strong>.<\/p>\n

This new, blank file is where you’ll write your code. Go ahead and save it now (File<\/strong> -> Save<\/strong>). It doesn’t matter where you save it or what you call it, but try to put it somewhere where you can find it again later.<\/p>\n

\"understanding-idle\"<\/a><\/p>\n

 <\/p>\n<\/div>\n

<\/div>\n<\/div>\n
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Our first expression in IDLE<\/h2>\n
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Let’s just get the hang of how IDLE works. In the new file you just created, type<\/p>\n

print(\"Hello world\")<\/code><\/p>\n

That means print the string inside the quotation marks<\/strong>. Save your document, and then, from the top menu, click on Run<\/strong> and then Run Module<\/strong>. This tells IDLE that you now want to execute the Python program you wrote.<\/p>\n

Look over at the shell. You should see the output of your program there.<\/p>\n

\"our-first-expression-in-idle\"<\/a><\/p>\n<\/div>\n

<\/div>\n<\/div>\n
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Our first real program!<\/h2>\n
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(Borrowed from\u00a0Automate the Boring Stuff with Python<\/em><\/a>.)<\/p>\n

Delete the contents of your file and copy and paste the following into the document:<\/p>\n

# This program says hello and asks for my name.\r\nprint('Hello world!')\r\nprint('What is your name?') \u00a0 \u00a0# ask for their name\r\nmyName = input()\r\nprint('It is good to meet you, ' + myName)\r\nprint('The length of your name is:')\r\nprint(len(myName))\r\nprint('What is your age?') \u00a0 \u00a0# ask for their age\r\nmyAge = input()\r\nprint('You will be ' + str(int(myAge) + 1) + ' in a year.')<\/pre>\n
Before you run this little program, let’s talk about what it’s doing. Read through the explanation contained in the image.<\/p>\n
If you don’t get it, put up a red flag, and we’ll talk you through it.<\/p>\n
\"Click<\/a>
Click on the image to see it full-size.<\/figcaption><\/figure>\n<\/div>\n
<\/div>\n<\/div>\n
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Run your program<\/h2>\n
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Save your file, and then from the top menu, click on Run<\/strong> and then Run module<\/strong>. If all goes well, you should be able to interact with the Python program you just created.<\/p>\n
\"run-your-program\"<\/a><\/p>\n<\/div>\n
<\/div>\n<\/div>\n
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Next steps<\/h2>\n
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That’s probably enough for today, but now you know the basics of writing a Python program! Because you’ve written your code in a file and saved it, you could in theory run it anytime you wanted.<\/p>\n
Of course, Python gets a lot more complicated, but it’s nothing you can’t handle. If you want to learn more, many people like Learn Python the Hard Way,<\/a><\/em> which is available for free online or for purchase as a book. I like Automate the Boring Stuff with Python<\/a><\/em> because it covers a lot of familiar tasks. Finally, many people have gotten up and running with humanities programming with the excellent Programming Historian<\/a>.<\/p>\n
If you prefer learning in person, you might be interested in joining PyLadies L.A.<\/a> (You don’t actually have to be a lady!) This is a welcoming group of people who are interested in fostering diversity and inclusion.<\/p>\n
When you’re learning to program, play and have fun. Take a break if you get overwhelmed and come back to it later. It takes time to absorb programming concepts, even though everyone’s always talking\u00a0about bootcamps and crash courses and the like.<\/p>\n
If we still have time left in class,<\/strong> take a look at chapter two of Automate the Boring Stuff with Python<\/a><\/em> and learn about control structures, one of the most important things to know about any kind of programming language.<\/p>\n<\/div>\n
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\"Control<\/a>
Control structures, oh my! Image from Automate the Boring Stuff with Python.<\/figcaption><\/figure>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"
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