#100DaysOfCode in Python Transcripts
Chapter: Appendix: Python language concepts
Lecture: Concept: If else
0:02 The most common control flow structure in programming has to be the "if" statement.
0:06 Let's see how we do "if" statements in Python.
0:09 Here we have a simple console program,
0:12 probably this bit of code is running in some kind of a loop or something like that,
0:15 and we are asking the user for input saying "what is your command?",
0:19 either list the items by typing L or exit from the program by hitting x.
0:23 And we capture that string and we say "if", so simple keyword "if"... some boolean test,
0:29 so in this case the command is == 'L'
0:32 so that means is the command equal to L: (colon)
0:34 and then define what we are going to do in that case.
0:37 In this case we are going to list the items, we could do multiple lines,
0:40 we are just doing one here.
0:42 Now we don't say "else if", in Python we say "elif", for short,
0:45 but then we just have another test,
0:48 so if it's not L and the command happens to be x, then we are going to exit.
0:51 And those are the two options that we are expecting,
0:54 but if we get something that we don't expect, like "hello there",
0:57 or empty enter or something like that,
1:00 we'll be in this final bit here where it says "Sorry, that wasn't understood".
1:04 So we start with "if" some kind of boolean expression, and remember,
1:08 we could just say "if" command: and leverage the truthiness of that value,
1:12 and that would run if they provided some kind of input at all,
1:15 but if we want to test for else, we say if command == 'L',
1:18 we have these additional as many as you want "else if" tests
1:21 and there is a final optional "else" clause.