Two of the basic building blocks of any Python script are numbers and strings.

A number in Python is just like what it is in the real world: one or more digits between 0 and 9 that collectively represent a numeric value. This collection of digits may be preceded by a negative sign (-) and may contain a decimal point. There are two basic types of numbers:

• Integers, or counting numbers, which are numbers that do not contain a decimal point;
• Floating point numbers, which are numbers that contain a decimal point.

Here are some simple examples of numbers:

714
0
-43
3.14159
-273.15

A string is a collection of zero or more symbols. These symbols (often called characters) can be any combination of letters, numbers, or anything else that can be displayed on a screen or stored in a file. Strings are normally enclosed in either double quotes (" ") or single quotes (' '). Here are some examples:

"Hello, world!"
'2 plus 2 equals 4'
"Python is #1"
'This string contains a lot of special characters: @#$&();:<>'
""

As you can see, each string in the above examples is surrounded by a pair of double quotes or a pair of single quotes. These quote characters enable Python to determine where a string begins and ends. Quote characters are not part of the string; they just enclose it. The last string in the list above, "", is called the empty string; it is a string of length zero.

If your string contains the character that you are using as the quote character, use a backslash (\) to indicate that the character is not a quote character:

"This string contains a word enclosed in \"quote\" characters"

This is stored in the computer as:

This string contains a word enclosed in "quote" characters

The backslash is also referred to as the escape character.

	If you want to put a backslash in a string, put another backslash in front of it: "This string contains \\ a backslash" The first backslash is the escape character for the second backslash.

To create a string in Unicode format, put a u character in front of the string:

u"This is a string in Unicode format"

To include a special character in the Unicode string, use \u followed by a four-digit number in hexadecimal format representing the numeric value of the character:

u"This string includes a Unicode 0020 character, which is a blank space: \u0020"

	For more information, see the Python documentation for Unicode strings.

It is important to remember that the number 714 and the string '714' are not the same thing in Python, though you can convert one to the other under certain conditions. String and numeric conversions will be discussed in the next section.