Regular expression to extract any 4 digit number starting beginning with 5 from a text file using python

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I am using the follwoing to extract any 4 digit number starting beginning with 5 from a text file using python:

regex = re.compile("^5\d{3}")

and this apparently looks only at the beginning of a line and doesn't look further until the end of the line to find the matches.

So for a sample string of "At this period by adding 52000 more particles we reched the value of 5810 threads per molecule." it shows no match.

What is wrong with my regular expression?

this regex will capture any 4 digit number starting with a 5 that has no beginning or trailing characters

^5\d{3}$

see it in action here

code:

regex = re.compile(r'^5\d{3}$')

Regular Expressions - PY4E, So far we have been reading through files, looking for patterns and extracting various Search for lines that start with 'From' import re hand = open('mbox-short .txt') for any number of times using the * or + characters in your regular expression. Jan 5 09:14:16 2008 Return-Path: <postmaster@collab. sakaiproject.org> for� A year is a 4-digit number, such as 2016 or 2017. With Python, we can single out digits of certain lengths. We extract only 4-digit numbers from a string. We can extract only 1-digit numbers or 2-digits numbers or 3-digit numbers or 4-digit numbers or 5-digits numbers, etc. We do this through the regular expression, regex= "\d{4}"

Just add a whitespace check to the regex expression

regex = re.compile(r'(5\d{3})(?=\s|$)')

This makes sure the number starts with 5 wherever in the text, has 3 subsequent numbers and has a whitespace character or end of string in front of it and return just the four digits.

Python Regular Expression, match() is very similar to re.search() difference is that it will start looking for matches at the beginning of the string. 1 2 3 4 5. import re s =� To understand how this regular expression works in Python, we begin with a simple example of a split function. In the example, we have split each word using the "re.split" function and at the same time we have used expression \s that allows to parse each word in the string separately.

regex = re.compile(r"\b(5\d{3})\b") is more exact

6.2. re — Regular expression operations — Python 3.4.10 , The solution is to use Python's raw string notation for regular expression Matches the start of the string, and in MULTILINE mode also matches For example, on the 6-character string 'aaaaaa', a{3,5} will match 5 'a' will match all the two-digits numbers from 00 to 59, and [0-9A-Fa-f] will match any hexadecimal digit. line2 = "hello 12 hi 89" temp1 = re.findall(r'\d+', line2) # through regular expression res2 = list(map(int, temp1)) print(res2) Hi , you can search all the integers in the string through digit by using findall expression . In the second step create a list res2 and add the digits found in string to this list . hope this helps . Regards, Diwakar

7.2. re — Regular expression operations — Python v3.1.5 , The solution is to use Python's raw string notation for regular expression patterns; For example, [^5] will match any character except '5', and [^^] will match any If the first digit of number is 0, or number is 3 octal digits long, it will not be using a regular expression beginning with '^': '^' matches only at the start of the� Approach: The idea is to use Python re library to extract the sub-strings from the given string which match the pattern [0-9]+.This pattern will extract all the characters which match from 0 to 9 and the + sign indicates one or more occurrence of the continuous characters.

Regular Expression HOWTO — Python 3.8.5 documentation, For example, the regular expression test will match the string test exactly. Some of the special sequences beginning with '\' represent predefined sets of Matches any non-digit character; this is equivalent to the class [^0-9] . \s To figure out what to write in the program code, start with the desired string to be matched. I am looking for a solution that can exclusively be done with a regular expression. I know this would be easy with variables, substrings, etc. And I am looking for PCRE style regex syntax even though I mention vim. I need to identify strings with 4 numeric digits, and they can't be all 0's. So the following strings would be a match:

Chapter 7 Pattern matching with regular expressions, In this chapter, you'll start by writing a program to find text patterns without using regular extract phone numbers and email addresses from a block of text. For example, a \d in a regex stands for a digit character—that is, any single numeral 0 to 9. Since (Ha){3,5} can match three, four, or five instances of Ha in the string� You can also specify a range of characters using -inside square brackets. [a-e] is the same as [abcde]. [1-4] is the same as [1234]. [0-39] is the same as [01239]. You can complement (invert) the character set by using caret ^ symbol at the start of a square-bracket. [^abc] means any character except a or b or c. [^0-9] means any non-digit

Comments
  • ^ anchors it to the start of the string.
  • Thanks, but now it finds two matches "52000" and "5810", although it should only find 4 digit numbers.
  • You need do indicate that there should be a non-digit character after the 3 digits: 5\d{3}[^\d]
  • But I don't want to copy the space character following the digit. Nor any other character.
  • try this \s(5[\d]{3})\s
  • No match found.
  • does this work if the string ends after the fourth digit?
  • That was a great point, edited accordingly. It now uses a lookahead to check if either has a whitespace or its end of string
  • Found a match without additional charachters!
  • So, working? You can always test it here: link