Command Line

[00:00:00]
>> Nina Zakharenko: I also wanna talk to you about how to write basic command line tools and scripts in Python. We wanna know how to accept command line arguments. It's pretty useful for a script, right? You want to interact with the user. We saw sys.argv. So that's one way of accepting input from,

[00:00:25]
>> Nina Zakharenko: Input from the user.
>> Nina Zakharenko: A nice trick for sys.argv, we can use slicing to remove the name of the file because we usually don't care about it, right? So I can say arguments equal, and where would I start my slice?
>> Nina Zakharenko: Which is the first value that we care about, at what index?

[00:00:52]
>> Speaker 2: One.
>> Nina Zakharenko: Index one, and go to the very end. We care about the rest of them. Now, if I,
>> Nina Zakharenko: Oops, I'm sorry. It was arguments sys.argv.
>> Nina Zakharenko: So I'll comment that out. Now, if I run this again,
>> Nina Zakharenko: We'll see that, okay, this is actually useful.

[00:01:18]
I didn't get any arguments. And now I can say, 123 hello goodbye, and it'll only print out the arguments that were actually useful to me.
>> Nina Zakharenko: Make a new file here, we're gonna call it,
>> Nina Zakharenko: Input_example.py.
>> Nina Zakharenko: To get and interact with user input, we can use the built-in input function in Python.

[00:01:52]
So I'm gonna say that name equals, call the built-in input function. And the argument here is what you want the prompt to look like. So say, Hello human, what is your name? Generally you wanna put a space here so that there's a little bit of spacing. You can even put a colon or something to kind of signify that you want some input here.

[00:02:20]
And then you can say, print out, hello, (name) nice to meet you!
>> Nina Zakharenko: Running this from the command palette, we'll see that my prompt has changed. It's a block now, it's waiting for input. So I can type my name in here and get my response back. Note that if you just press Enter, you'll get back an empty string.

[00:02:58]
So when you're accepting user input, it's generally a good idea to do some validation on it or some syntax checking.