Reading strings and numbers into an array

Question

Thanks guys, that really helped. My main problem as you all pointed out was that I had 4 white spaces rather than a tab!

I have a textfile of the format:

string001    124.342
string002    235.111
string003    552.145

With a blank line at the bottom.

I just want to read this into an array. I thought that the best way to do this would be loadtxt from numpy, but when this didn't work, I went for genfromtxt, but couldn't quite get it to work either. This is what I have as my latest effort:

y = np.genfromtxt('1400list.txt',delimiter="\t", dtype=[('mystring','S10'),('myint','i8')])

print y

But I get the error:

rows = np.array(data, dtype=[('', _) for _ in dtype_flat])
ValueError: size of tuple must match number of fields.

Could anyone please help me to figure this one out?

Thank you!

What language are you using? Add a tag for the language if you want help! — mortb
– mortb, Commented Sep 5, 2012 at 7:38

Vicent · Accepted Answer · 2012-09-05 16:41:03Z

2

Your code works fine here (although I suppose you want to use float dtype instead of integer one) with Python 2.7 and numpy 1.5.1:

#!/usr/bin/env python
import numpy

y = numpy.genfromtxt('1400list.txt', delimiter='\t',dtype=[('A', 'S10'),
('B', 'i8')])
print y

The output is:

vicent@deckard:/tmp$ python prova.py 
[('string001', 124L) ('string002', 235L) ('string003', 552L)]
vicent@deckard:/tmp$

Please, make sure that you are using tabs instead of spaces in your data file.

answered Sep 5, 2012 at 16:41

Vicent

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tobias_k · Accepted Answer · 2012-09-05 08:01:22Z

0

This should work:

f = open("text.txt")
items = []
for line in f.readlines():
    arr = line.split("    ")
    if len(arr) == 2:
        items.append((arr[0], float(arr[1])))
f.close()

Note that the numbers are floats, not ints. Also note that the last line has no entry, thus the if len(arr) == 2.

answered Sep 5, 2012 at 8:01

tobias_k

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Pierre GM · Accepted Answer · 2012-09-05 19:16:37Z

0

Make sure you have the proper delimiter, that is, that your different columns are actually separated by tabulations and not hard spaces.

As an alternative, you could also use a tuple of integers as delimiters, if your initial file has some fixed formatting. In your case, that would be using

np.genfromtxt("text.txt", delimiter=(14,7), dtype=[('mystring','S10'),('myint','float')])

(Note that I corrected your dtype, using a float for the second element). The documentation will give you more details.

answered Sep 5, 2012 at 19:16

Pierre GM

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