1.7 Itse1359-1040-strings part 1

An expression using literals

On the other hand, the following expression describes the sum of two literal numeric values:

sum = 6 + 8

No matter when this expression is evaluated, it will always produce a sum of 14.

String literals

Literal values can also be used for strings. For example, the interactive code fragment in Figure 1 shows

• My name entered three times, in three different ways, on the interactive command line.
• The output from the interpreter for each entry.

The first two entries are valid string literals. As you can see, in the first two cases, the interpreter displays my name in the output.

Note that in the first two cases, my name is surrounded by either quotes (sometimes called double quotes) or apostrophes (sometimes called single quotes) .

A syntax error

However, the third entry is not a valid string literal, and the interactive interpreter produced a SyntaxError message. (Although not shown in Figure 1 , the IDLE GUI interface highlighted my last name with a red backgroundimmediately above the SyntaxError message.) In the third case, my name is not surrounded by either double quotes or single quotes, and that is what causedthe error.

A valid string literal

Referring to String and Bytes literals , the Python Language Reference states:

Both types of literals can be enclosed in matching single quotes (') or double quotes (").

This explains why the first two input lines in the interactive code fragment in Figure 1 were accepted and the third input line produced an error.

Proper syntax

In the first input line in Figure 1 , my name was surrounded by matching double quotes. In the second input line, my name was surrounded by matching single quotes.

Bad syntax

However, in the third input line, my name was not surrounded by quotes of either type and this produced a syntax error.

More examples

Figure 2 shows two more examples of valid string literals.

The top half of Figure 2 was produced by the IDLE GUI interface. The bottom half was independently produced by the Python command-line interface.I included both of them to show you the output format difference between the two interfaces. In both cases, I pressed the Enter key following the input that reads """Dick.

Triple-quoted strings

Referring again to String and Bytes literals, the earlier quotation from the Python Language Reference goes on to state:

They can also be enclosed in matching groups of three single or double quotes (these are generally referred to as triple-quoted strings ). The backslash (\) character is used to escape characters that otherwise have aspecial meaning, such as newline, backslash itself, or the quote character.

Further down that same page we find: