Beginning Python - From Novice to Professional

CHAPTER 1 ■ INSTANT HACKING: THE BASICS 23
It’s always a good idea to make your code readable on its own as well, even without the
comments. Luckily, Python is an excellent language for writing readable programs.
Strings
Now what was all that raw_input and "Hello, " + name + "!" stuff about? Let’s tackle the
"Hello" part first and leave raw_input for later.
The first program in this chapter was simply
print "Hello, world!"
It is customary to begin with a program like this in programming tutorials—the problem is that I
haven’t really explained how it works yet. Well, you know the basics of the print statement (I’ll have
more to say about that later), but what is "Hello, world!"? It’s called a string (as in “a string of characters”).
Strings are found in almost every useful, real-world Python program and have many uses,
the main one being to represent a bit of text, such as the exclamation “Hello, world!”
Single-Quoted Strings and Escaping Quotes
Strings are values, just like numbers are:
>>> "Hello, world!"
'Hello, world!'
There is one thing that may be a bit surprising about this example, though: When Python
printed out our string, it used single quotes, whereas we used double quotes. What’s the difference?
Actually, there is no difference:
>>> 'Hello, world!'
'Hello, world!'
Here, too, we use single quotes, and the result is the same. So why allow both? Because in some
cases it may be useful:
>>> "Let's go!"
"Let's go!"
>>> '"Hello, world!" she said'
'"Hello, world!" she said'
In the preceding code, the first string contains a single quote (or apostrophe, as we should
perhaps call it in this context), and therefore we can’t use single quotes to enclose the string.
If we did, the interpreter would complain (and rightly so):
>>> 'Let's go!'
SyntaxError: invalid syntax
Here, the string is 'Let', and Python doesn’t quite know what to do with the following s (or the
rest of the line, for that matter).
In the second string, we use double quotes as part of our sentence. Therefore, we have to
use single quotes to enclose our string, for the same reasons as stated previously. Or, actually