Assume I have a string which includes some data fields that are separated by "|", like
|1|2|3|4|5|6|7|8|
My purpose is to get the 8th field. This is what I'm doing:
pattern = re.compile(r'^\s+(\|.*?\|){8}')
match = pattern.match(test_line)
if match:
print:match.group(8)
But looks like it can not match. I know in this case I need to use ? for non-greedy match, but why I can not get the 8th field?
Thanks
Regex might be complicating this problem rather than simplifying it. A simple way to get an eighth item from a | delimited string is using split():
a = '|here|is|some|data|separated|by|bars|hooray!|'
print a.split('|')[8]
RETURNS
hooray!
Using regex, one way to get it would be:
import re
a = '|here|is|some|data|separated|by|bars|hooray!|'
pattern = re.compile(r'([^\|]+)')
match = pattern.findall(a)
print match[7]
RETURNS
hooray!
Related
I have a string in which there are some attributes that may be empty:
[attribute1=value1, attribute2=, attribute3=value3, attribute4=]
With python I need to sobstitute the empty values with the value 'None'. I know I can use the string.replace('=,','=None,').replace('=]','=None]') for the string but I'm wondering if there is a way to do it using a regex, maybe with the ?P<name> option.
You can use
import re
s = '[attribute1=value1, attribute2=, attribute3=value3, attribute4=]'
re.sub(r'=(,|])', r'=None\1', s)
\1 is the match in parenthesis.
With python's re module, you can do something like this:
# import it first
import re
# your code
re.sub(r'=([,\]])', '=None\1', your_string)
You can use
s = '[attribute1=value1, attribute2=, attribute3=value3, attribute4=]'
re.sub(r'=(?!\w)', r'=None', s)
This works because the negative lookahead (?!\w) checks if the = character is not followed by a 'word' character. The definition of "word character", in regular expressions, is usually something like "a to z, 0 to 9, plus underscore" (case insensitive).
From your example data it seems all attribute values match this. It will not work if the values may start with something like a comma (unlikely), may be quoted, or may start with anything else. If so, you need a more fool proof setup, such as parse from the start: skipping the attribute name by locating the first = character.
Be specific and use a character class:
import re
string = "[attribute1=value1, attribute2=, attribute3=value3, attribute4=]"
rx = r'\w+=(?=[,\]])'
string = re.sub(rx, '\g<0>None', string)
print string
# [attribute1=value1, attribute2=None, attribute3=value3, attribute4=None]
I have a regex "value=4020a345-f646-4984-a848-3f7f5cb51f21"
if re.search( "value=\w*|\d*\-\w*|\d*\-\w*|\d*\-\w*|\d*\-\w*|\d*", x ):
x = re.search( "value=\w*|\d*\-\w*|\d*\-\w*|\d*\-\w*|\d*\-\w*|\d*", x )
m = x.group(1)
m only gives me 4020a345, not sure why it does not give me the entire "4020a345-f646-4984-a848-3f7f5cb51f21"
Can anyone tell me what i am doing wrong?
try out this regex, looks like you are trying to match a GUID
value=[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}
This should match what you want, if all the strings are of the form you've shown:
value=((\w*\d*\-?)*)
You can also use this website to validate your regular expressions:
http://regex101.com/
The below regex works as you expect.
value=([\w*|\d*\-\w*|\d*\-\w*|\d*\-\w*|\d*\-\w*|\d*]+)
You are trying to match on some hex numbers, that is why this regex is more correct than using [\w\d]
pattern = "value=([0-9a-fA-F]{8}-([0-9a-fA-F]{4}-){3}[0-9a-fA-F]{12})"
data = "value=4020a345-f646-4984-a848-3f7f5cb51f21"
res = re.search(pattern, data)
print(res.group(1))
If you dont care about the regex safety, aka checking that it is correct hex, there is no reason not to use simple string manipulation like shown below.
>>> data = "value=4020a345-f646-4984-a848-3f7f5cb51f21"
>>> print(data[7:])
020a345-f646-4984-a848-3f7f5cb51f21
>>> # or maybe
...
>>> print(data[7:].replace('-',''))
020a345f6464984a8483f7f5cb51f21
You can get the subparts of the value as a list
txt = "value=4020a345-f646-4984-a848-3f7f5cb51f21"
parts = re.findall('\w+', txt)[1:]
parts is ['4020a345', 'f646', '4984', 'a848', '3f7f5cb51f21']
if you really want the entire string
full = "-".join(parts)
A simple way
full = re.findall("[\w-]+", txt)[-1]
full is 4020a345-f646-4984-a848-3f7f5cb51f21
value=([\w\d]*\-[\w\d]*\-[\w\d]*\-[\w\d]*\-[\w\d]*)
Try this.Grab the capture.Your regex was not giving the whole as you had used | operator.So if regex on left side of | get satisfied it will not try the latter part.
See demo.
http://regex101.com/r/hQ1rP0/45
I have a set of strings like this:
uc001acu.2;C1orf159;chr1:1046736-1056736;uc001act.2;C1orf159;
I need to extract the sub-string between two semicolons and I only need the first occurrence.
The result should be: C1orf159
I have tried this code, but it does not work:
import re
info = "uc001acu.2;C1orf159;chr1:1046736-1056736;uc001act.2;C1orf159;"
name = re.search(r'\;(.*)\;', info)
print name.group()
Please help me.
Thanks
You can split the string and limit it to two splits.
x = info.split(';',2)[1]
import re
pattern=re.compile(r".*?;([a-zA-Z0-9]+);.*")
print pattern.match(info).groups()
This looks for first ; eating up non greedily through .*? .Then it captures the alpha numeric string until next ; is found.Then it eats up the rest of the string.Match captured though .groups()
I'm trying to match a pattern against strings that could have multiple instances of the pattern. I need every instance separately. re.findall() should do it but I don't know what I'm doing wrong.
pattern = re.compile('/review: (http://url.com/(\d+)\s?)+/', re.IGNORECASE)
match = pattern.findall('this is the message. review: http://url.com/123 http://url.com/456')
I need 'http://url.com/123', http://url.com/456 and the two numbers 123 & 456 to be different elements of the match list.
I have also tried '/review: ((http://url.com/(\d+)\s?)+)/' as the pattern, but no luck.
Use this. You need to place 'review' outside the capturing group to achieve the desired result.
pattern = re.compile(r'(?:review: )?(http://url.com/(\d+))\s?', re.IGNORECASE)
This gives output
>>> match = pattern.findall('this is the message. review: http://url.com/123 http://url.com/456')
>>> match
[('http://url.com/123', '123'), ('http://url.com/456', '456')]
You've got extra /'s in the regex. In python the pattern should just be a string. e.g. instead of this:
pattern = re.compile('/review: (http://url.com/(\d+)\s?)+/', re.IGNORECASE)
It should be:
pattern = re.compile('review: (http://url.com/(\d+)\s?)+', re.IGNORECASE)
Also typically in python you'd actually use a "raw" string like this:
pattern = re.compile(r'review: (http://url.com/(\d+)\s?)+', re.IGNORECASE)
The extra r on the front of the string saves you from having to do lots of backslash escaping etc.
Use a two-step approach: First get everything from "review:" to EOL, then tokenize that.
msg = 'this is the message. review: http://url.com/123 http://url.com/456'
review_pattern = re.compile('.*review: (.*)$')
urls = review_pattern.findall(msg)[0]
url_pattern = re.compile("(http://url.com/(\d+))")
url_pattern.findall(urls)
I am wanting to verify and then parse this string (in quotes):
string = "start: c12354, c3456, 34526; other stuff that I don't care about"
//Note that some codes begin with 'c'
I would like to verify that the string starts with 'start:' and ends with ';'
Afterward, I would like to have a regex parse out the strings. I tried the following python re code:
regx = r"start: (c?[0-9]+,?)+;"
reg = re.compile(regx)
matched = reg.search(string)
print ' matched.groups()', matched.groups()
I have tried different variations but I can either get the first or the last code but not a list of all three.
Or should I abandon using a regex?
EDIT: updated to reflect part of the problem space I neglected and fixed string difference.
Thanks for all the suggestions - in such a short time.
In Python, this isn’t possible with a single regular expression: each capture of a group overrides the last capture of that same group (in .NET, this would actually be possible since the engine distinguishes between captures and groups).
Your easiest solution is to first extract the part between start: and ; and then using a regular expression to return all matches, not just a single match, using re.findall('c?[0-9]+', text).
You could use the standard string tools, which are pretty much always more readable.
s = "start: c12354, c3456, 34526;"
s.startswith("start:") # returns a boolean if it starts with this string
s.endswith(";") # returns a boolean if it ends with this string
s[6:-1].split(', ') # will give you a list of tokens separated by the string ", "
This can be done (pretty elegantly) with a tool like Pyparsing:
from pyparsing import Group, Literal, Optional, Word
import string
code = Group(Optional(Literal("c"), default='') + Word(string.digits) + Optional(Literal(","), default=''))
parser = Literal("start:") + OneOrMore(code) + Literal(";")
# Read lines from file:
with open('lines.txt', 'r') as f:
for line in f:
try:
result = parser.parseString(line)
codes = [c[1] for c in result[1:-1]]
# Do something with teh codez...
except ParseException exc:
# Oh noes: string doesn't match!
continue
Cleaner than a regular expression, returns a list of codes (no need to string.split), and ignores any extra characters in the line, just like your example.
import re
sstr = re.compile(r'start:([^;]*);')
slst = re.compile(r'(?:c?)(\d+)')
mystr = "start: c12354, c3456, 34526; other stuff that I don't care about"
match = re.match(sstr, mystr)
if match:
res = re.findall(slst, match.group(0))
results in
['12354', '3456', '34526']