I have data of the form
CS989_-RED814298959
CS663_RED812657324
RED819238322_CS537
......
This data is in csv file. I want to retrieve all the sub strings starting with RED. Please suggest me a way to do this using regular expression in python
I tried following code:
import re
string="RED819238322_CS537"
substring=re.match("[a-zA-Z]*//([0-9]*)",string)
It's returning None
If you don't need regex, don't use regex.
with open('myfile') as f:
print([l for l in f if l.startswith('RED')])
changing as necessary, i.e. with csv.reader:
with open('myfile') as f:
print([row for row in csv.reader(f) if row[0].startswith('RED')])
Help on function match in module re:
match(pattern, string, flags=0) Try to apply the pattern at the start of the string, returning a match object, or None if no match was found.
You want re.search or re.findall instead. Also your regexp is incorrect - if what you want is just "RED" followed by any number of digits, it's spelled r"RED[0-9]+"
>>> strings
['CS989_-RED814298959', 'CS663_RED812657324', 'RED819238322_CS537']
>>> re.match(r"(RED[0-9]+)", strings[0])
>>> re.findall(r"(RED[0-9]+)", strings[0])
['RED814298959']
>>> re.findall(r"(RED[0-9]+)", strings[1])
['RED812657324']
>>> re.findall(r"(RED[0-9]+)", strings[2])
['RED819238322']
>>> re.search(r"(RED[0-9]+)", strings[0])
<_sre.SRE_Match object at 0x1772e40>
What are those slashes doing in there? Try this:
substring=re.match("[a-zA-Z]*([0-9]*)", string)
//in your data, why do you expect this to match?