Read lines starting with numbers

Question

How can I only read lines in a file that start with numbers in python i.e

Hello World <--ignore
Lovely day
blah43 
blah
1234 <--read
blah12 <--ignore
blah 
3124 <--read
Not matter how many words there are <--ignore
blah 
0832 8423984 234892304 8239048324 8023948<--read
blah132 <--ignore

score 11 · Accepted Answer · edited Dec 17 '14 at 09:22

11

import re
with open("filename") as f:
    for line in f:
        if re.match(r"^\d+.*$",line):
            print line

edited Dec 17 '14 at 09:22

Gareth Latty

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answered Dec 17 '14 at 09:21

vks

67,027
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1

Edit to use [the `with` statement to open the file](http://www.youtube.com/watch?v=lRaKmobSXF4), as is best practice. – Gareth Latty Dec 17 '14 at 09:23

Mazdak · Answer 2 · 2014-12-17T09:28:51.100

5

you can use isdigit() function :

for line in open('f.txt','r'):
   if line[0].isdigit():
       print line

edited Dec 17 '14 at 09:28

answered Dec 17 '14 at 09:22

Mazdak

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Note that `isdigit()` has what might be a surprising definition of a digit, which may or may not be valid for the use case at hand. It includes all the numbers you would expect, but also [some unicode characters you might not](http://stackoverflow.com/questions/10604074/python-isdigit-function-return-true-for-non-digit-character-u-u2466). – Gareth Latty Dec 17 '14 at 09:24
isdigit is used for test that a string start with a number ? – Hacketo Dec 17 '14 at 09:25
@Hacketo When applied to the first character, as here, yes. – Gareth Latty Dec 17 '14 at 09:26
@Hacketo `isdigit()` Return true if all characters in the string are digits and there is at least one character, false otherwise – Mazdak Dec 17 '14 at 09:27

Read lines starting with numbers

2 Answers2