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Read file from line 2 or skip header row

How can I skip the header row and start reading a file from line2?


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

if you need the header later, instead of next(f) use f.readline() and store it as a variable
Or use header_line = next(f).
myone complains 'file' object is not an iterator if I use next(f) approach. Instead the f.readline() worked.
@soMuchToLearnAndShare Which python version did you use? It's better to provide information for reproducing the error.
c
chriscauley
f = open(fname,'r')
lines = f.readlines()[1:]
f.close()

This will skip 1 line. ['a', 'b', 'c'][1:] => ['b', 'c']
@LjubisaLivac is right - this answer generalises to any line, so this is a much more powerful solution.
This is fine UNTIL the file is too large to read. This is fine for small files.
The slice also builds a copy of the contents. This is just unnecessarily inefficient.
What about using consume() from more-itertools as stated in docs.python.org/3/library/itertools.html#itertools-recipes ? I heard about this on stackoverflow.com/questions/11113803
s
saimadhu.polamuri

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

It is not necessary to assign readline() to a variable if one does not need this line. I like this solution most, however.
Mixing direct reads with using the file as an iterator isn't recommended (although in this specific case no harm is done).
V
Vajk Hermecz

If slicing could work on iterators...

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

This is a really nice and pythonic way of solving the problem and can be extended to an arbitrary number of header lines
This is a really nice execution!
Marvellous solution
This should be upvoted much, much more than it currently is.
This solution is really good. This even works for in-memory uploaded file while iterating over file object.
D
Dror Hilman
f = open(fname).readlines()
firstLine = f.pop(0) #removes the first line
for line in f:
    ...

This will read the entire file into memory at once, so it's only practical if you're reading a fairly small file.
M
Minh Tran

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.


T
Tiago Martins Peres

If you want to read multiple CSV files starting from line 2, this works like a charm

for files in csv_file_list:
        with open(files, 'r') as r: 
            next(r)                  #skip headers             
            rr = csv.reader(r)
            for row in rr:
                #do something

(this is part of Parfait's answer to a different question)


A
Aran-Fey
# Open a connection to the file
with open('world_dev_ind.csv') as file:

    # Skip the column names
    file.readline()

    # Initialize an empty dictionary: counts_dict
    counts_dict = {}

    # Process only the first 1000 rows
    for j in range(0, 1000):

        # Split the current line into a list: line
        line = file.readline().split(',')

        # Get the value for the first column: first_col
        first_col = line[0]

        # If the column value is in the dict, increment its value
        if first_col in counts_dict.keys():
            counts_dict[first_col] += 1

        # Else, add to the dict and set value to 1
        else:
            counts_dict[first_col] = 1

# Print the resulting dictionary
print(counts_dict)