1.4.8.1 In Python

Within a Python string, certain sequences have special meaning. Each of these sequences begins with a backslash \, known as the escape character. The values (and different escape methods) allowed in string literals are described in the Python documentation at http://www.python.org/doc/current/ref/strings.html. This is a brief summary.

\\  	Backslash (\)  	
\' 	Single quote (') 	
\" 	Double quote (") 	
\a 	ASCII Bell (BEL) 	
\b 	ASCII Backspace (BS) 	
\f 	ASCII Formfeed (FF) 	
\n 	ASCII Linefeed (LF) 	
\N{name} 	Character named name in the Unicode database (Unicode only) 	
\r 	ASCII Carriage Return (CR) 	
\t 	ASCII Horizontal Tab (TAB) 	
\uxxxx 	Character with 16-bit hex value xxxx (Unicode only)
\Uxxxxxxxx 	Character with 32-bit hex value xxxxxxxx (Unicode only)
\v 	ASCII Vertical Tab (VT) 	
\ooo 	Character with octal value ooo 
\xhh 	Character with hex value hh

You can use these characters in SQL exactly the same way as you would in Python. For example 'end of one line\nstart of new line' is a valid SQL string containing a line break in the middle and could be used like this:

cursor.execute("INSERT INTO table (columnOne) VALUES ('end of one line\nstart of new line')")

There is one important point to note about how Python (and hence web.database ) deals with these escape characters. If a string contains a backslash \ but the character after the backslash is not a character which can be escaped then the single backslash is treated as a single backslash. If the character can be used in an escape sequence then the backslash is treated as an escape character and the character is escaped.

Note: All examples in this section are from the Python prompt not the web.database one.

Python 2.4 (#60, Nov 30 2004, 11:49:19) [MSC v.1310 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> print 'hello\%world'
hello\%world
>>> print 'hello\nworld'
hello
world
>>>

If a string contains both escaped and non-escaped characters Python guesses which are backslashes and which are escape characters:

>>> print 'hello\nworld\%again'
hello
world\%again
>>>

If a string contains a double backslash \\ it is always treated as an escaped backslash character and printed as \.

>>> print '\\%'
\%
>>> print '\%'
\%

>>> print '\\%' == '\%'
True
>>>

>>> print '\\\\%' == '\\%'
False
>>>

When writing Python strings you have to be very careful how the backslash character is being used and then you will have no problems.