Python Programming for Biology: Bioinformatics and Beyond

Escape sequences

The following are some of the most commonly used escape sequences  in  Python,  which

allow  you  to  specify  textual  characters  or  control  codes  when  they  are  not  available  as

regular symbols.

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Code

Description

Example

\

A backslash character, which needs to be

forced when the following character would

otherwise form an escape code.

text = ‘\title’

Text is ‘\title’ and does

not have a tab (\t) code

inside.

'

A single quote, which may need to be escaped

in situations where it should not be considered

as the start or end of a string.

text = ‘Don't do that!’

Note: not required

when a string is defined

with double quotes.

"

A double quote, which may need to be escaped

in situations where it should not be considered

as the start or end of a string.

text = “Shout "Help!"

loudly.”

Note: not required

when a string is defined

with single quotes.

\n

A newline (linefeed) control character. Used to

separate lines of text in Unix- and Linux-based

computers

text = ‘Line A\nLine

B\n’

Text value is split into

two lines on Linux and

Unix machines.

\r

A carriage return control character. Used in

combination with \n on Windows-based

systems to separate lines of text.

text = “Line A\r\nLine

B\r\n”

Text is split into two

lines on Windows

machines.

\t

A tab character, providing indentation with

whitespace to pre-set stop points.

text = ‘Col 1\tCol

2\tCol 3\n’

Tabs indent to form

three columns.

\u….

Specifies a Unicode character using a 16-bit

hexadecimal value.

text = u’\u03b1-helix’

Creates ‘α-helix’, e.g.

for graphical displays.

\x..

Specifies a character using a hexadecimal

value.

text =

‘\x48\x65\x6C\x6C\x6f’

Text is hexadecimal

code for ‘Hello’.

Constants

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The  following  are  the  commonly  used  named  constants.  From  Python  3  these  become

keywords, and thus are a reserved part of the language and may not be redefined.