find all occurrences of a substring in a string python regex

How to find all occurrences of a substring?

stackoverflow.com › questions › 4664850 › how-to-find-all-occurrences-of-a-substring

There is no simple built-in string function that does what you're looking for, but you could use the more powerful regular expressions:

import re
[m.start() for m in re.finditer('test', 'test test test test')]
#[0, 5, 10, 15]

If you want to find overlapping matches, lookahead will do that:

[m.start() for m in re.finditer('(?=tt)', 'ttt')]
#[0, 1]

If you want a reverse find-all without overlaps, you can combine positive and negative lookahead into an expression like this:

search = 'tt'
[m.start() for m in re.finditer('(?=%s)(?!.{1,%d}%s)' % (search, len(search)-1, search), 'ttt')]
#[1]

re.finditer returns a generator, so you could change the [] in the above to () to get a generator instead of a list which will be more efficient if you're only iterating through the results once.

Answer from moinudin on Stack Overflow

Stack Overflow

stackoverflow.com › questions › 4664850 › how-to-find-all-occurrences-of-a-substring

python - How to find all occurrences of a substring? - Stack Overflow

Top answer

1 of 16

818

There is no simple built-in string function that does what you're looking for, but you could use the more powerful regular expressions:

import re
[m.start() for m in re.finditer('test', 'test test test test')]
#[0, 5, 10, 15]

If you want to find overlapping matches, lookahead will do that:

[m.start() for m in re.finditer('(?=tt)', 'ttt')]
#[0, 1]

If you want a reverse find-all without overlaps, you can combine positive and negative lookahead into an expression like this:

search = 'tt'
[m.start() for m in re.finditer('(?=%s)(?!.{1,%d}%s)' % (search, len(search)-1, search), 'ttt')]
#[1]

2 of 16

188

>>> help(str.find)
Help on method_descriptor:

find(...)
    S.find(sub [,start [,end]]) -> int

Thus, we can build it ourselves:

def find_all(a_str, sub):
    start = 0
    while True:
        start = a_str.find(sub, start)
        if start == -1: return
        yield start
        start += len(sub) # use start += 1 to find overlapping matches

list(find_all('spam spam spam spam', 'spam')) # [0, 5, 10, 15]

No temporary strings or regexes required.

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reddit.com › r/learnpython › how to find all occurrences of a substring in a string while ignore some characters in python?

r/learnpython on Reddit: How to find all occurrences of a substring in a string while ignore some characters in Python?

July 25, 2024 -

I'd like to find all occurrences of a substring while ignore some characters. How can I do it in Python?

Example:

long_string = 'this is a t`es"t. Does the test work?'
small_string = "test"
chars_to_ignore = ['"', '`']
print(find_occurrences(long_string, small_string))

should return [(10, 16), (27, 31)] because we want to ignore the presence of chars ` and ".

(10, 16) is the start and end index of t`es"t in long_string,
(27, 31) is the start and end index of test in long_string.

Top answer

1 of 5

You could use re for this. ex import re long_string = 'this is a t`es"t. Does the test work?' small_string = "test" chars_to_ignore = ['"', '`'] print(re.findall(f"[{''.join(chars_to_ignore)}]*".join(small_string), long_string))

2 of 5

Replace the not-wanted characters in a copy of the string, replacing with an empty string / removing, and then search. Instead of trying to come up with all of the exception characters, copy characters that are a letter, or a number if you want them, to a new string.

Discussions

Python Regex: Extract all occurences of a substring within a string - Stack Overflow

I am trying to extract all occurrences of a substring within a string using Python Regex. This is what I have tried: import re line = "The dimensions of the first rectangle: 10'x20', second More on stackoverflow.com

stackoverflow.com

How can I find all exact occurrences of a string, or close matches of it, in a longer string in Python?

This is a regex operation. You can match exact with some_substring in full_string Then find the index. But partial matches is going to require a lot of code or a regex expression. More on reddit.com

r/learnpython

May 9, 2024

Python regex when string contains any word from a list of words AND any word from another list

Use lookaheads. ^(?=.*foo|.*bar|.*Python)(?=.*me|.*you|.*we)

Add \b around the words (e.g. \bfoo\b) if you want them as isolated words, otherwise you get matches like fool)

https://regex101.com/r/dnqSjr/1

Top answer

1 of 3

You may use this regex:

r"\d+['\"]?x\d+['\"]?(?:\s*[a-zA-Z]+)?"

RegEx Demo

Code:

>>> import re
>>> line = "The dimensions of the first rectangle: 10'x20', second rectangle: 10x35cm, third rectangle: 30x35cm"
>>> print (re.findall(r"\d+['\"]?x\d+['\"]?(?:\s*[a-zA-Z]+)?", line))
["10'x20'", '10x35cm', '30x35cm']

RegEx Details:

\d+: Match 1+ digits
['\"]?: Match optional ' or "
x: Match letter x
\d+: Match 1+ digits
['\"]?: Match optional ' or "
(?:\s*[a-zA-Z]+)?: Match optional units comprising 1+ letters

2 of 3

You can do this without regex using split:

In [1089]: m = [i.split(':')[1].strip() for i in line.split(',')]

In [1090]: m
Out[1090]: ["10'x20'", '10x35cm', '30x35cm']

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Stack Abuse

stackabuse.com › python-count-number-of-substring-occurrences-in-string

Python: Count Number of Substring Occurrences in String

March 28, 2023 - Original string is: John has 1 apple, Sarah has 2 apples, Mike has 5 apples. Substring is: apples Number of substring occurrences is: 2 Starting indices of substrings are: [30, 49] The finditer() function is part of Python's RegEx library - re.

JanBask Training

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How to find all occurrences of a substring? | JanBask Training Community

July 18, 2021 - Python has string.find() and string.rfind() to get the index of a substring in a string. I'm wondering whether there is something like string.find_all() which can return all found indexes (not only the first from the beginning or the first from the end). ... string = "test test test test" print string.find('test') # 0 print string.rfind('test') # 15 #this is the goal print string.find_all('test') # [0,5,10,15] ... To find all occurrences of a substring in a string Python does not have any built-in string function that does what you're looking for, but you could use the more powerful regular expressions:

Finxter

blog.finxter.com › home › learn python blog › 5 best ways to find all occurrences of a substring in a list of strings with python

5 Best Ways to Find All Occurrences of a Substring in a List of Strings with Python - Be on the Right Side of Change

March 5, 2024 - strings = ['apple pie', 'banana pie', 'apple tart'] substring = 'apple' occurrences = [(index, string.find(substring)) for index, string in enumerate(strings) if substring in string] print(occurrences) ... By employing a list comprehension, this snippet not only checks for the presence of the substring using the in operator but also calls the find() method on the string to obtain the exact starting position of the substring. Regular expressions provide a powerful way to search for patterns. By using Python’s re module, you can find complex patterns within strings.

CodeSignal

codesignal.com › learn › courses › practicing-string-operations-and-type-conversions-in-python › lessons › exploring-substring-search-in-python-strings

Exploring Substring Search in Python Strings

Python string objects have a built-in method called str.find(substring, starting_index=0), which comes in handy here. It returns the lowest index of the substring in str that is greater than or equal to starting_index if found. Otherwise, it returns -1. for original, substring in zip(orig_strs, ...

Quora

quora.com › How-do-you-find-the-occurrences-of-a-substring-in-a-string-in-Python

How to find the occurrences of a substring in a string in Python - Quora

Answer: Suppose you have a string >>> str = ‘now is the time for all good men to come to the aid of their country’ then >>> str.find('all') 20 ‘all’ starts at str[20] To find all the ‘to’ substrings, you need ‘regular expressions’. That’s too complicated to go into here.

CodeRivers

coderivers.org › blog › python-find-all-occurrences-in-string

Python: Finding All Occurrences in a String - CodeRivers

February 22, 2026 - This code works in a similar way ... re module in Python allows us to use regular expressions. To find all occurrences of a substring, we can use the finditer() function....

DataCamp

datacamp.com › tutorial › python-string-contains

Python String Search and Replace: in, .find(), .index(), .count(), and .replace() | DataCamp

March 31, 2026 - Use .index() when the substring must exist and an exception is the right failure mode. product = "USB-C Cable" print(product.index("Cable")) # 6 try: product.index("HDMI") except ValueError: print("Required label missing") .count() returns the number of non-overlapping occurrences.

DaniWeb

daniweb.com › programming › software-development › threads › 475566 › how-to-find-all-occurrences-of-a-substring-in-a-string-python

how to find all occurrences of a substring in a string python

March 19, 2014 - This complements @Gribouillis’s regex fix while providing a simple non-regex solution that directly answers @sruthiashok’s request. Use re.findall() — Gribouillis 1,391 Jump to Post ... We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge. Sign Up — It's Free! ... Libcurl C++ CURLE_FAILED_INIT. SSH Error -43. 6 · Extracting Faces from Videos Using Python Deepface Library 0

LabEx

labex.io › tutorials › python-how-to-use-re-findall-in-python-to-find-all-matching-substrings-415132

How to use re.findall() in Python to find all matching substrings | LabEx

## Using re.findall() to find all occurrences of "Python" matches = re.findall(r"Python", text) ## Print the results print("Original text:") print(text) print("\nMatches found:", len(matches)) print("Matching substrings:", matches) ... Original text: Python is amazing. Python is versatile. I love learning Python programming. Matches found: 3 Matching substrings: ['Python', 'Python', 'Python'] ... The r before the string denotes a raw string, which is recommended when working with regular expressions

Sololearn

sololearn.com › en › Discuss › 2144485 › is-it-possible-to-find-the-index-of-all-occurrences-of-a-substring-in-a-a-string-in-python

Is it possible to find the index of all occurrences of a substring in a a string in python? | Sololearn: Learn to code for FREE!

It gives you the index of the found string. You can tell it where to start looking. Then write a little loop, find all the indexes and put them in a list. Nice little practice task. Since the RegEx solution is already given, and it's nicely short anyway, let me add the more lengthy builtin style version for reference: occurrences = [] word = 'abracadabra' i = 0 while True: f = word.find('abr', i) if f==-1: break occurrences.append(f) i = f+1 print(occurrences)

Finxter

blog.finxter.com › 5-best-ways-to-find-all-occurrences-of-a-substring-within-a-list-of-strings-in-python

5 Best Ways to Find All Occurrences of a Substring within a List of Strings in Python – Be on the Right Side of Change

The outer list comprehension aggregates these lists into a list of lists, making it clear where each occurrence is found within the input list. Regular expressions are powerful for string searching. Python’s re.finditer() method returns an iterator yielding match objects over all non-overlapping ...

reddit.com › r/learnpython › how can i find all exact occurrences of a string, or close matches of it, in a longer string in python?

r/learnpython on Reddit: How can I find all exact occurrences of a string, or close matches of it, in a longer string in Python?

May 9, 2024 -

Goal:

I'd like to find all exact occurrences of a string, or close matches of it, in a longer string in Python.
I'd also like to know the location of these occurrences in the longer string.
To define what a close match is, I'd like to set a threshold, e.g. number of edits if using the edit distance as the metric.
I'd also like the code to give a matching score (the one that is likely used to determine if a candidate substring is over the matching threshold I set).

How can I do so in Python?

Example:

long_string = """1. Bob likes classical music very much.
2. This is classic music!
3. This is a classic musical. It has a lot of classical musics.
"""

query_string = "classical music"

I'd like the Python code to find "classical music" and possibly "classic music", "classic musical" and "classical musics" depending on the string matching threshold I set.

Research: I found Checking fuzzy/approximate substring existing in a longer string, in Python? but the question focuses on the best match only (i.e., not all occurrences) and answers either also focuses on the best match or don't work on multi-word query strings (since the question only had a single-word query strings, or return some incorrect score (doesn't get a perfect score even for an exact match).

Top answer

1 of 3

This is a regex operation. You can match exact with some_substring in full_string Then find the index. But partial matches is going to require a lot of code or a regex expression.

2 of 3

Did you read this answer to the question? https://stackoverflow.com/a/30654059 It lets you access multiple matches.