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In Python, strings are objects, just like everything is an object.

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We are going to take a little bit of time and look at what this means, because

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this is not what people are used to who have been programming in other

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programming languages.

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But in Python, the "everything is an object" paradigm has particular impact on how

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we operate on strings.

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And also, it's a little bit different than it was in Python 2.

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Even though strings were objects in Python 2, they weren't fully first class

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objects in the sense that they are in Python 3, and the interface is a lot more

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consistent in Python 3, but it also means that it's significantly different

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than it was in Python 2.

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So if you're familiar with Python 2, this is worth paying attention to just a little bit.

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So here we have a string, 'this is a string,' and the value of that of course is a string.

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Now, if we assign it to a variable, now we have a variable, and if we just get

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the value of that variable, it says, "This is a string."

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Now, of course in Python a variable is just a reference to an object.

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So I can operate on that string by saying s.upper() and and we get the

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uppercase of the string.

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And here is the thing that surprises people sometimes is I can do the same

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thing just on the string, I can say 'This is a string'.upper(), and that

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will give me the uppercase of THIS IS A STRING., because the string itself is an object.

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The significant impact here is the use of the format method.

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The format method is very often called on an bare string, so to speak.

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So it's very common to do something like this in Python.

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This is a string and put in a format, and close the quotes, and say .format(42)

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like that, and the result will be 'This is a string 42', because what we have

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done is we actually operated on the string using the format method, and

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replaced the token in the string with the formatted number 42, and this is very common to do.

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Older versions of Python, it was common to do something like, 'This is a string

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%d' and then use the % operator and say 42 like that, and that worked exactly

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the same way, because you weren't using the dot notation to access a method.

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Instead it overloading this % operator to do exactly the same thing.

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Now, it's worth noting that in Python 3 that % notation is considered

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obsolescent, which means that in future versions of Python that will no

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longer be supported.

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So this is a good time to get used to using the .format method, and in

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fact, the format method is a lot more powerful and a lot more consistent in its syntax.

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The syntax used in the old percent style string replacement was borrowed from C,

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and it's 40 years old, and while it certainly works and it's certainly familiar

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to anybody with the background in the C programming language,

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it's not as consistent or as powerful as the new format operator in the format language.

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So we will be talking more about that in detail later on in this chapter.

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For now, what's important to note is that a string is an object and a

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variable containing a string is really just a variable that contains a

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reference to a string object.

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So everything that you can do on that string object, you can do on the string

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itself, because the string itself is the string object.