Python Jumpstart by Building 10 Apps Transcripts
Chapter: App 2: Guess that number game
Lecture: Concept: Shape of Python code (blocks and suites)

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0:00 A core concept of this application
0:02 is to understand the shape of a Python program.
0:05 So far, until very recently,
0:07 we've been just writing straight top to bottom code,
0:11 with no blocks, no functions,
0:14 no conditionals or loops
0:15 or anything that has to be disambiguated in that sense.
0:19 And now, what I want to focus on
0:21 is this concept of a shape of the Python program.
0:24 Everything you see on the screen that is in the square,
0:27 the gray square, the blue squares, the purple squares,
0:30 those are all separate code blocks,
0:32 sometimes called code suites in Python
0:35 that are executed in some particular manner.
0:37 The blue blocks are functions
0:39 that are executed when the functions are called,
0:41 the purple blocks are if or else blocks
0:44 that are executed depending on whether the argument is batch or something else.
0:48 The key thing that defines code blocks in Python
0:52 which makes it quite unique in this regard, is white space.
0:56 Many C derived languages use curly braces, think of Javascript,
1:01 C#, Swift, those types of languages, they all use curly braces
1:06 and when you open the curly brace that begins a block of code,
1:09 and when you close curly brace that block code is now done.
1:12 It doesn't work this way in Python,
1:14 it's all about the indentation,
1:15 so you can see the gray block which is just the overall program
1:19 and we have two functions we are defining,
1:22 we have def main and we say colon,
1:25 and then we indent all the body of this function.
1:28 And that body is made up of those two blocks in there,
1:31 there is two purple blocks sort of the if else statement.
1:34 Then we unindent and we define another run function
1:36 the details don't matter, we say colon and indent again
1:39 and that's the body of the function for a run.
1:42 So you've already seen previously that editors like PyCharm
1:46 and other Python intelligent editors know about this shape,
1:50 they know about this code blocks
1:52 and if you type if something colon enter,
1:54 it will automatically indent and stay intended
1:57 until you unintend it manually.
1:59 While it might seem a little challenging to use spaces to define a structure,
2:04 it turns out the editors know all about it and make it super easy.
2:08 One more comment I should add
2:09 while we are talking about indentation or white space,
2:12 tabs? tabs are not a good idea, in Python,
2:15 Python does not like tabs.
2:17 This white space should be actual the space character, not tabs,
2:23 now that doesn't mean that you don't press tab in your editor like in PyCharm
2:26 if you hit tab it will indent but it actually just means
2:29 it's going to insert four spaces for you
2:32 and many of the Python editors are like that.
2:35 So if you are coming to Python from another language
2:37 that does not use significant white space like C++
2:41 or some of the C based languages
2:43 this could feel a little strange to you and it does take a week or so
2:47 to really become super comfortable with this idea but once you do
2:51 it's very natural and it's a lovely way to program
2:55 but I know that some of you out there you are thinking WOW!
2:58 this is really different and to you I say
3:00 just give it a try, use a nice editor and you will start to love it right away.
3:05 if this feels totally natural and good to you,
3:07 well then you are going to love Python right from the beginning.