CODEWITHSUNDEEP
pythonnumpy
Ada Xu
Ada Xu

Reputation: 983

ignoring string while reading into an array

I am trying to load a .csv file into an array. However, the file looks something like this. 

"myfilename",0.034353453,-1.234556,-3,45671234
,1.43567896, -1.45322124, 9.543422
 .................................
 .................................

I am trying to skip the leading string. I've been doing away with the first row till now. 

 a = np.genfromtxt(file,delimiter=',',skiprows=1)

But I was wondering if there's a way to read into an array ignoring the string at the beginning in processing.

Upvotes: 1

Views: 1589

Answers (2)

Chris
Chris

Reputation: 430

Can you just use loadtxt(..., usecols=(1,2,3), ...), which avoids skipping a line at the start of the file?

The usecols argument just tells loadtxt which columns to extract (and are numeric)

# Put data into file (in shell, just me copying the sample)
cat >> /tmp/data.csv
"myfilename",0.034353453,-1.234556,-3,45671234
,1.43567896, -1.45322124, 9.543422

# In IPython
In [1]: import numpy as np

In [2]: a = np.loadtxt('/tmp/data.csv', usecols=(1,2,3), delimiter=',')

In [3]: a
Out[3]: 
array([[ 0.03435345, -1.234556  , -3.        ],
       [ 1.43567896, -1.45322124,  9.543422  ]])

Upvotes: 2

mgilson
mgilson

Reputation: 309899

since it's just the first line at the beginning of the file, you could write a helper generator to remove that string for now:

def helper(filename):
    with open(filename) as fin:
        # this could get more robust ... e.g. by doing typechecking if necessary.
        line = next(fin).split(',')
        yield ','.join(line[1:])
        for line in fin:
            yield line

arr = np.genfromtxt(helper('myfile.csv'), delimiter=',')

Upvotes: 0

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