python find all strings starting and ending with certain characters [duplicate] - python

This question already has an answer here:
Find all strings that are in between two sub strings
(1 answer)
Closed last month.
How can I extract with python all strings starting with 'a[' and ending with ']'?
for example
str= "a[0]*x**3+a[13]"
result : a[0], a[13]
thanks


We can use re.findall here:
inp = "a[0]*x**3+a[13]"
matches = re.findall(r'\ba\[.*?\]', inp)
print(matches) # ['a[0]', 'a[13]']

Related

How to get the numbers from a string (contains no spaces between letters and numbers)? [duplicate]

This question already has answers here:
How to extract numbers from a string in Python?
(19 answers)
Closed 3 years ago.
So, I have a string "AB256+74POL". I want to extract the numbers only into a list say num = [256,74]. How to do this in python?
I have tried string.split('+') and followed by iterating over the two parts and adding the characters which satisfy isdigit(). But is there an easier way to that?

import re
a = 'AB256+74POL'
array = re.findall(r'[0-9]+', a)

"".join([c if c.isdigit() else " " for c in mystring]).split()
Explanation
Strings are iterable in python. So we iterate on each character in the string, and replace non digits with spaces, then split the result to get all sequences of digits in a list.

Split the string into words [duplicate]

This question already has answers here:
Split string every nth character?
(19 answers)
Closed 4 years ago.
how to split a string into words of 2 letters. Like given string is "HelloThere" now i want to make it ["He","ll","oT","he","re"]. Please help to code that in python.

yourList = []
yourString = "HelloThere"
while yourString:
yourList.append(yourString[:2])
yourString = yourString[2:]
If you print yourList, you will get the result.

What is wrong with this Python regular expression? [duplicate]

This question already has answers here:
re.findall behaves weird
(3 answers)
Closed 4 years ago.
Given a string, I want to find all the substrings consisting of two or three '4,'.
For example, given '1,4,3,2,1,1,4,4,3,2,1,4,4,3,2,1,4,4,4,3,2,'
I want to get ['4,4,', '4,4,', '4,4,4'].
str_ = '1,4,4,3,2,1,1,4,4,3,2,1,4,4,3,2,1,4,4,3,2,'
m = re.findall(r"(4,){2,3}", str_)
what I get is :
['4,', '4,', '4,', '4,']
what's wrong?
It seems to me that the parenthesis wrapping '4,' is interpreted as grouping but not telling Python '4' and ',' should occur together. However, I don't know how to do this.

Just use non-capturing group (online version of this regex here):
import re
s = '1,4,3,2,1,1,4,4,3,2,1,4,4,3,2,1,4,4,4,3,2,'
print(re.findall(r'(?:4,?){2,3}', s))
Prints:
['4,4,', '4,4,', '4,4,4,']
EDIT:
Edited regex to capture 2 or 3 elements "4,"

How to remove a character from a string until certain index? [duplicate]

This question already has answers here:
Remove characters from beginning and end or only end of line
(5 answers)
Closed 4 years ago.
So, I have the following string "........my.python.string" and I want to remove all the "." until it gets to the first alphanumeric character, is there a way to achieve this other than converting the string to a list and work it from there?

You can use re.sub:
import re
s = "........my.python.string"
new_s = re.sub('^\.+', '', s)
print(new_s)
Output:
my.python.string

Capture repeated characters and split using Python [duplicate]

This question already has answers here:
How can I tell if a string repeats itself in Python?
(13 answers)
Closed 3 years ago.
I need to split a string by using repeated characters.
For example:
My string is "howhowhow"
I need output as 'how,how,how'.
I cant use 'how' directly in my reg exp. because my input varies. I should check the string whether it is repeating the character and need to split that characters.

import re
string = "howhowhow"
print(','.join(re.findall(re.search(r"(.+?)\1", string).group(1), string)))
OUTPUT
howhowhow -> how,how,how
howhowhowhow -> how,how,how,how
testhowhowhow -> how,how,how # not clearly defined by OP
The pattern is non-greedy so that howhowhowhow doesn't map to howhow,howhow which is also legitimate. Remove the ? if you prefer the longest match.

lengthofRepeatedChar = 3
str1 = 'howhowhow'
HowmanyTimesRepeated = int(len(str1)/lengthofRepeatedChar)
((str1[:lengthofRepeatedChar]+',')*HowmanyTimesRepeated)[:-1]
'how,how,how'
Works When u know the length of repeated characters

Categories

Resources