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Regular Expression Examples in Python
Literal characters
| Sr.No. | Example & Description |
|---|---|
| 1 |
python Matches beginning of line. |
Character classes
| Sr.No. | Example & Description |
|---|---|
| 1 |
[Pp]ython Match "Python" or "python" |
| 2 |
rub[ye] Match "ruby" or "rube" |
| 3 |
[aeiou] Match any one lowercase vowel |
| 4 |
[0-9] Match any digit; same as [0123456789] |
| 5 |
[a-z] Match any lowercase ASCII letter |
| 6 |
[A-Z] Match any uppercase ASCII letter |
| 7 |
[a-zA-Z0-9] Match any of the above |
| 8 |
[^aeiou] Match anything other than a lowercase vowel |
| 9 |
[^0-9] Match anything other than a digit |
Special Character Classes
| Sr.No. | Example & Description |
|---|---|
| 1 |
. Match any character except newline |
| 2 |
\d Match a digit: [0-9] |
| 3 |
\D Match a nondigit: [^0-9] |
| 4 |
\s Match a whitespace character: [ \t\r\n\f] |
| 5 |
\S Match nonwhitespace: [^ \t\r\n\f] |
| 6 |
\w Match a single word character: [A-Za-z0-9_] |
| 7 |
\W Match a nonword character: [^A-Za-z0-9_] |
Repetition Cases
| Sr.No. | Example & Description |
|---|---|
| 1 |
ruby? Match "rub" or "ruby": the y is optional |
| 2 |
ruby* Match "rub" plus 0 or more ys |
| 3 |
ruby+ Match "rub" plus 1 or more ys |
| 4 |
\d{3} Match exactly 3 digits |
| 5 |
\d{3,} Match 3 or more digits |
| 6 |
\d{3,5} Match 3, 4, or 5 digits |
Nongreedy repetition
This matches the smallest number of repetitions −
| Sr.No. | Example & Description |
|---|---|
| 1 |
<.*> Greedy repetition: matches "<python>perl>" |
| 2 |
<.*?> Nongreedy: matches "<python>" in "<python>perl>" |
Grouping with Parentheses
| Sr.No. | Example & Description |
|---|---|
| 1 |
\D\d+ No group: + repeats \d |
| 2 |
(\D\d)+ Grouped: + repeats \D\d pair |
| 3 |
([Pp]ython(, )?)+ Match "Python", "Python, python, python", etc. |
Backreferences
This matches a previously matched group again −
| Sr.No. | Example & Description |
|---|---|
| 1 |
([Pp])ython&\1ails Match python&pails or Python&Pails |
| 2 |
(['"])[^\1]*\1 Single or double-quoted string. \1 matches whatever the 1st group matched. \2 matches whatever the 2nd group matched, etc. |
Alternatives
| Sr.No. | Example & Description |
|---|---|
| 1 |
python|perl Match "python" or "perl" |
| 2 |
rub(y|le)) Match "ruby" or "ruble" |
| 3 |
Python(!+|\?) "Python" followed by one or more ! or one ? |
Anchors
This needs to specify match position.
| Sr.No. | Example & Description |
|---|---|
| 1 |
^Python Match "Python" at the start of a string or internal line |
| 2 |
Python$ Match "Python" at the end of a string or line |
| 3 |
\APython Match "Python" at the start of a string |
| 4 |
Python\Z Match "Python" at the end of a string |
| 5 |
\bPython\b Match "Python" at a word boundary |
| 6 |
\brub\B \B is nonword boundary: match "rub" in "rube" and "ruby" but not alone |
| 7 |
Python(?=!) Match "Python", if followed by an exclamation point. |
| 8 |
Python(?!!) Match "Python", if not followed by an exclamation point. |
Updated on: 2020-01-31T07:51:02+05:30
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