Apply String Methods (Solution)

00:00 I’ve already assigned the four strings here to save a bit of time, and now the task is to make them all return True when calling .startswith() passing in "be" as an argument.

00:19 For string1, we can see that it’s capitalized, so it starts with an uppercase "B", which is why initially calling .startswith("be") on it returned False.

00:26 So I will just lowercase this one saying string1 .lower() and then call .startswith("be"). And you can see that this returns True. Note also that in this case I didn’t print the output,

00:41 which if you’re running this in a script, you would have to, but since I’m in a REPL, I can skip the print() call and just instead see the output displayed here in the REPL directly. string2.

00:52 Well, here I don’t need to do anything, so I can just say .startswith("be"), and I’ll get True. And I’m going to go and copy this because otherwise I’m going to keep making mistakes typing it out.

01:17 Now we’re looking at string number three, which is an all-uppercase word that is "BEAR" in this case. So again, I will need to lowercase it so I can say string3 .lower() and then .startswith("be").

01:31 And as you can see here, I’m kind of, like, chaining these method calls on it. This doesn’t always work, but it works with strings because strings are immutable.

01:41 So all of these methods always return a new string. So string3.lower() actually returns a new string. It’s not the same string3, but it’s 'bear' but lowercase.

01:51 Let’s try it out.

01:56 So you get 'bear' back. And then because string3.lower() returns this lowercase string 'bear', I can then call .startswith("be") on this lowercase string.

02:08 So I’m not actually calling .startswith("be") on the uppercase "BEAR" but on the new string that gets created when I run string3.lower().

02:13 Putting one method

02:17 after another with a dot in between is something that’s called method chaining.

02:24 Again, we’ve got one more to go, string four. string4. I will need to get rid of the whitespace, so I’m going to say .lstrip() and get rid of the whitespace on the left side.

02:39 There’s none on the right side. And then I will also need to lowercase it, so .lstrip().lower(), and then I’m going to do .startswith("be"),

02:52 and I get True as a return value. So this is kind of interesting to look at, right? You can see all these dots and then method calls after it, like I explained with the one before. You’re doing the same here.

03:07 Just there’s one additional step. So in this case, you’re first creating a string that has the whitespace removed on the left side, so it’s still this weirdly cased "bEautiful" with the with the capital "E" and the rest lowercase.

03:21 Then you create a new string with also adding .lower() at the end of this, which then gets rid of the uppercase "E". Well, it converts it to a lowercase "e".

03:32 And then finally, you’re calling .startswith("be") on this string, on the lowercase "beautiful" string. And because of that, it returns True, and that’s it.

03:43 If you did this with intermediate variables, that’s completely fine as well. Like I explained the steps here, you could have done that as well. You could have said string4_without_whitespace and assigned it to string4.lstrip() and then say string4_without_whitespace.lower() is going to be s4_lower.

04:16 And then you could say s4_lower .startswith("be").

04:23 Oh no, I got a double dot in there accidentally. s4_lower.startswith("be"), and then you get True. So, you don’t need to do this using method chaining in one line.

04:36 You can do it with intermediate variables, and that’s totally fine, but it also works like this, but maybe it’s interesting to see. Exercise solved.