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Read file from line 2 or skip header row

Tags:

python

file-io

with open(fname) as f:
    next(f)
    for line in f:
        #do something

f = open(fname,'r')
lines = f.readlines()[1:]
f.close()

If you want the first line and then you want to perform some operation on file this code will helpful.

with open(filename , 'r') as f:
    first_line = f.readline()
    for line in f:
            # Perform some operations

If slicing could work on iterators...

from itertools import islice
with open(fname) as f:
    for line in islice(f, 1, None):
        pass

f = open(fname).readlines()
firstLine = f.pop(0) #removes the first line
for line in f:
    ...

To generalize the task of reading multiple header lines and to improve readability I'd use method extraction. Suppose you wanted to tokenize the first three lines of coordinates.txt to use as header information.

Example

coordinates.txt
---------------
Name,Longitude,Latitude,Elevation, Comments
String, Decimal Deg., Decimal Deg., Meters, String
Euler's Town,7.58857,47.559537,0, "Blah"
Faneuil Hall,-71.054773,42.360217,0
Yellowstone National Park,-110.588455,44.427963,0

Then method extraction allows you to specify what you want to do with the header information (in this example we simply tokenize the header lines based on the comma and return it as a list but there's room to do much more).

def __readheader(filehandle, numberheaderlines=1):
    """Reads the specified number of lines and returns the comma-delimited 
    strings on each line as a list"""
    for _ in range(numberheaderlines):
        yield map(str.strip, filehandle.readline().strip().split(','))

with open('coordinates.txt', 'r') as rh:
    # Single header line
    #print next(__readheader(rh))

    # Multiple header lines
    for headerline in __readheader(rh, numberheaderlines=2):
        print headerline  # Or do other stuff with headerline tokens

Output

['Name', 'Longitude', 'Latitude', 'Elevation', 'Comments']
['String', 'Decimal Deg.', 'Decimal Deg.', 'Meters', 'String']

If coordinates.txt contains another headerline, simply change numberheaderlines. Best of all, it's clear what __readheader(rh, numberheaderlines=2) is doing and we avoid the ambiguity of having to figure out or comment on why author of the the accepted answer uses next() in his code.