Regular Expressions 2 Flashcards
What is a regular expression?
A regular expression, regex or regexp, is a sequence of characters that define a search pattern.
What does [A-Z] mean?
Any character from A to Z
e.g [0-9] 0,1,2..9
[a-d] a,b,c,d
What does \s mean?
Any whitespace character (tab \t, space, new-line \n)
What does \w mean?
Any alphanumeric character
What does \b mean?
Stands for a word boundary
What does \d mean?
Stands for a digit (= [0-9] )
What does {x,y} do?
{x,y} specifies the number of repeats of a previous item
a{1,3} matches a, aa ,and aaa, but not aaaa
a{1,} means 1 or more a
What does ^[ ] mean?
^ at the beginning [ ] matches all characters specified in the group at the start of a line or given sentence
What does [^ ] mean?
When [^inside brackets], it means “not”.
What does $ do?
$ matches the end of a text
What does ^ do?
^ matches the start of a text
What does . mean?
. (dot) is the wildcard symbol (any letter)
What does ? mean?
? specifies that the previous character is optional
What does + and * mean? And what are they called?
• + matches one or more of the preceding character (or range) • * matches zero or more of the preceding character (or group) • + and * are called (Kleene) closures
What does \D \S \W mean?
\D Any non-digit character, equivalent to [^0-9]
\S Any non-whitespace character, equivalent to [^\t\n\r\f\v]
\W Any non-alphanumeric character, equivalent to [^a-zA-Z0-9_]
What does \t \n mean?
\t The tab character
\n The newline character
What does re.search(pattern, text) do?
Check whether exists any
match of the pattern in
the text
What does re.split(pattern, text) do?
Splits the text according to
certain rules
What does re.findall(pattern, text) do?
Finds all occurrences of
text matching the pattern
