regex for repeating words in a string in Python - python

I have a good regexp for replacing repeating characters in a string. But now I also need to replace repeating words, three or more word will be replaced by two words.
Like
bye! bye! bye!
should become
bye! bye!
My code so far:
def replaceThreeOrMoreCharachetrsWithTwoCharacters(string):
# pattern to look for three or more repetitions of any character, including newlines.
pattern = re.compile(r"(.)\1{2,}", re.DOTALL)
return pattern.sub(r"\1\1", string)

Assuming that what is called "word" in your requirements is one or more non-whitespaces characters surrounded by whitespaces or string limits, you can try this pattern:
re.sub(r'(?<!\S)((\S+)(?:\s+\2))(?:\s+\2)+(?!\S)', r'\1', s)

You could try the below regex also,
(?<= |^)(\S+)(?: \1){2,}(?= |$)
Sample code,
>>> import regex
>>> s = "hi hi hi hi some words words words which'll repeat repeat repeat repeat repeat"
>>> m = regex.sub(r'(?<= |^)(\S+)(?: \1){2,}(?= |$)', r'\1 \1', s)
>>> m
"hi hi some words words which'll repeat repeat"
DEMO

I know you were after a regular expression but you could use a simple loop to achieve the same thing:
def max_repeats(s, max=2):
last = ''
out = []
for word in s.split():
same = 0 if word != last else same + 1
if same < max: out.append(word)
last = word
return ' '.join(out)
As a bonus, I have allowed a different maximum number of repeats to be specified (the default is 2). If there is more than one space between each word, it will be lost. It's up to you whether you consider that to be a bug or a feature :)

Try the following:
import re
s = your string
s = re.sub( r'(\S+) (?:\1 ?){2,}', r'\1 \1', s )
You can see a sample code here: http://codepad.org/YyS9JCLO

def replaceThreeOrMoreWordsWithTwoWords(string):
# Pattern to look for three or more repetitions of any words.
pattern = re.compile(r"(?<!\S)((\S+)(?:\s+\2))(?:\s+\2)+(?!\S)", re.DOTALL)
return pattern.sub(r"\1", string)

Related

Python re regex sub letters not surrounded in quotes and not if they match specific word including regex group / match

I need to sub letters not surrounded in quotes and not if they match the word TODAY with a particular string where a part of it includes the match group e.g.
import re
import string
s = 'AB+B+" HELLO"+TODAY()/C* 100'
x = re.sub(r'\"[^"]*\"|\bTODAY\b|([A-Z]+)', r'a2num("\g<0>")', s)
print (x)
expected output:
'a2num("AB")+a2num("B")+" HELLO"+TODAY()/a2num("C")* 100'
actual output:
'a2num("AB")+a2num("B")+a2num("" HELLO"")+a2num("TODAY")()/a2num("C")* 100'
I am nearly there but it is not obeying the quote rules or the TODAY word rule, I know the string doesn't make any sense but it's just a harsh test of the regex
Your regex approach is correct but you need to use a lambda function in re.sub
>>> s = 'AB+B+" HELLO"+TODAY()/C* 100'
>>> rs = re.sub(r'"[^"]*"|\bTODAY\b|\b([A-Z]+)\b',
... lambda m: 'a2num("' + m.group(1) + '")' if m.group(1) else m.group(), s)
>>> print (rs)
a2num("AB")+a2num("B")+" HELLO"+TODAY()/a2num("C")* 100
Code Demo

Python Find entire word in string using regex and user input

I'm trying to find the entire word exactly using regex but have the word i'm searching for be a variable value coming from user input. I've tried this:
regex = r"\b(?=\w)" + re.escape(user_input) + r"\b"
if re.match(regex, string_to_search[i], re.IGNORECASE):
<some code>...
but it matches every occurrence of the string. It matches "var"->"var" which is correct but also matches "var"->"var"iable and I only want it to match "var"->"var" or "string"->"string"
Input: "sword"
String_to_search = "There once was a swordsmith that made a sword"
Desired output: Match "sword" to "sword" and not "swordsmith"
You seem you want to use a pattern that matches an entire string. Note that \b word boundary is needed when you wan to find partial matches. When you need a full string match, you need anchors. Since re.match anchors the match at the start of string, all you need is $ (end of string position) at the end of the pattern:
regex = '{}$'.format(re.escape(user_input))
and then use
re.match(regex, search_string, re.IGNORCASE)
You can try re.finditer like that:
>>> import re
>>> user_input = "var"
>>> text = "var variable var variable"
>>> regex = r"(?=\b%s\b)" % re.escape(user_input)
>>> [m.start() for m in re.finditer(regex, text)]
[0, 13]
It'll find all matches iteratively.

How can I "divide" words with regular expressions?

I have a sentence in which every token has a / in it. I want to just print what I have before the slash.
What I have now is basic:
text = less/RBR.....
return re.findall(r'\b(\S+)\b', text)
This obviously just prints the text, how do I cut off the words before the /?
Assuming you want all characters before the slash out of every word that contains a slash. This would mean e.g. for the input string match/this but nothing here but another/one you would want the results match and another.
With regex:
import re
result = re.findall(r"\b(\w*?)/\w*?\b", my_string)
print(result)
Without regex:
result = [word.split("/")[0] for word in my_string.split()]
print(result)
Simple and straight-forward:
rx = r'^[^/]+'
# anchor it to the beginning
# the class says: match everything not a forward slash as many times as possible
In Python this would be:
import re
text = "less/RBR....."
print re.match(r'[^/]+', text)
As this is an object, you'd probably like to print it out, like so:
print re.match(r'[^/]+', text).group(0)
# less
This should also work
\b([^\s/]+)(?=/)\b
Python Code
p = re.compile(r'\b([^\s/]+)(?=/)\b')
test_str = "less/RBR/...."
print(re.findall(p, test_str))
Ideone Demo

Remove a character in string if it doesn't belong to a group of matching pattern in Python

If I have a string such that it contains many words. I want to remove the closing parenthesis if the word in the string doesn't start with _.
Examples input:
this is an example to _remove) brackets under certain) conditions.
Output:
this is an example to _remove) brackets under certain conditions.
How can I do that without splitting the words using re.sub?
re.sub accepts a callable as the second parameter, which comes in handy here:
>>> import re
>>> s = 'this is an example to _remove) brackets under certain) conditions.'
>>> re.sub('(\w+)\)', lambda m: m.group(0) if m.group(0).startswith('_') else m.group(1), s)
'this is an example to _remove) brackets under certain conditions.'
I wouldn't use regex here when a list comprehension can do it.
result = ' '.join([word.rstrip(")") if not word.startswith("_") else word
for word in words.split(" ")])
If you have possible input like:
someword))
that you want to turn into:
someword)
Then you'll have to do:
result = ' '.join([word[:-1] if word.endswith(")") and not word.startswith("_") else word
for word in words.split(" ")])

Regex? Match part of or whole word

I was wondering if it's possible to use regex with python to capture a word, or a part of the word (if it's at the end of the string).
Eg:
target word - potato
string - "this is a sentence about a potato"
string - "this is a sentence about a potat"
string - "this is another sentence about a pota"
Thanks!
import re
def get_matcher(word, minchars):
reg = '|'.join([word[0:i] for i in range(len(word), minchars - 1, -1)])
return re.compile('(%s)$' % (reg))
matcher = get_matcher('potato', 4)
for s in ["this is a sentence about a potato", "this is a sentence about a potat", "this is another sentence about a pota"]:
print matcher.search(s).groups()
OUTPUT
('potato',)
('potat',)
('pota',)
Dont know how to match a regex in python, but the regex would be:
"\bp$|\bpo$|\bpot$|\bpota$|\bpotat$|\bpotato$"
This would match anything from p to potato if its the last word in the string, and also for example not something like "foopotato", if this is what you want.
The | denotes an alternative, the \b is a "word boundary", so it matches a position (not a character) between a word- and a non-word character. And the $ matches the end of the string (also a position).
Use the $ to match at the end of a string. For example, the following would match 'potato' only at the end of a string (first example):
"potato$"
This would match all of your examples:
"pota[to]{1,2}$"
However, some risk of also matching "potao" or "potaot".
import re
patt = re.compile(r'(p|po|pot|pota|potat|potato)$')
patt.search(string)
I was tempted to use r'po?t?a?t?o?$', but that would also match poto or pott.
No, you can't do that with a regex as far as I know, without pointless (p|po|pot ...) matches which are excessive. Instead, just pick off the last word, and match that using a substring:
match = re.search('\S+$', haystack)
if match.group(0) == needle[:len(match.group(0))]:
# matches.

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