Regex Syntax¶
Characters¶| Character | Matches |
|---|
a | a character |
. | Any character (except newline) |
. | . character |
| |
* | * character |
Regex Cheat Sheet ¶ Regex Syntax¶. I send out 1 Python exercise every week through a Python skill-building service called Python Morsels. Regular expressions (regex or regexp) are extremely useful in extracting information from any text by searching for one or more matches of a specific search pattern (i.e. A specific sequence of. Regular Expressions with Python Regular Expressions Cheat Sheet Object Types - Lists Object Types - Dictionaries and Tuples Functions def,.args,.kargs Functions lambda Built-in Functions map, filter, and reduce Decorators List Comprehension Sets (union/intersection) and itertools - Jaccard coefficient and shingling to check plagiarism.
Character Classes¶| Matches | Description |
|---|
[abcd] | Any one of the letters a through d | Set of characters |
[^abcd] | Any character but a, b, c, or d | Complement of a set of characters |
[a-d] | Any one of the letters a through d | Range of characters |
[a-dz] | Any of a, b, c, d, or z | Range of characters |
Special Sequences¶| Type | Expression | Equivalent To | Description |
|---|
| Word Character | w | [a-zA-Z0-9_] | Alphanumeric or underscore |
|---|
| Non-word Character | W | [^a-zA-Z0-9_] | Anything but a word character |
|---|
| Digit Character | d | [0-9] | Numeric |
|---|
| Non-digit Character | D | [^0-9] | Non-numeric |
|---|
| Whitespace Character | s | [tnrfv] | Whitespace |
|---|
| Non-whitespace Character | S | [^tnrfv] | Anything but a whitespace character |
|---|
Anchors¶| Anchor | Matches |
|---|
^ | Start of the string |
$ | End of the string |
b | Boundary between word and non-word characters |
Groups¶| Group Type | Expression |
|---|
| Capturing | ( ... ) |
| Non-capturing | (?: ... ) |
Quantifiers/Repetition¶| Quantifier | Modification |
|---|
{5} | Match expression exactly 5 times |
{2,5} | Match expression 2 to 5 times |
{2,} | Match expression 2 or more times |
{,5} | Match expression 0 to 5 times |
* | Match expression 0 or more times |
{,} | Match expression 0 or more times |
? | Match expression 0 or 1 times |
{0,1} | Match expression 0 or 1 times |
+ | Match expression 1 or more times |
{1,} | Match expression 1 or more times |
Non-greedy quantifiers¶| Quantifier | Modification |
|---|
{2,5}? | Match 2 to 5 times (less preferred) |
{2,}? | Match 2 or more times (less preferred) |
{,5}? | Match 0 to 5 times (less preferred) |
*? | Match 0 or more times (less preferred) |
{,}? | Match 0 or more times (less preferred) |
?? | Match 0 or 1 times (less preferred) |
{0,1}? | Match 0 or 1 times (less preferred) |
+? | Match 1 or more times (less preferred) |
{1,}? | Match 1 or more times (less preferred) |
Alternators¶| Quantifier | Modification |
|---|
ABC|DEF | Match string ABC or string DEF |
Lookaround¶| Quantifier | Modification |
|---|
(?=abc) | Zero-width match confirming abc will match upcoming chars |
(?!abc) | Zero-width match confirming abc will not match upcoming chars |
Cheat Sheet For Regex In Python
Python¶
functions¶| Function | Purpose | Usage |
|---|
re.search | Return a match object if pattern found in string | re.search(r'[pat]tern','string') |
re.finditer | Return an iterable of match objects (one for each match) | re.finditer(r'[pat]tern','string') |
re.findall | Return a list of all matched strings (different when capture groups) | re.findall(r'[pat]tern','string') |
re.split | Split string by regex delimeter & return string list | re.split(r'[-]','st-ring') |
re.compile | Compile a regular expression pattern for later use | re.compile(r'[pat]tern') |
Regex In Python Cheat Sheet Pdf
flags¶| Flag | Description |
|---|
re.IGNORECASE | Match uppercase and lowercase characters interchangeably |
re.VERBOSE | Ignore whitespace characters and allow # comments |