numpy.loadtxt

numpy.loadtxt(fname, dtype=<type 'float'>, comments='#', delimiter=None, converters=None, skiprows=0, usecols=None, unpack=False)

Load data from a text file.

Each row in the text file must have the same number of values.

Parameters:

fname : file or string

File or filename to read. If the filename extension is .gz or .bz2, the file is first decompressed.

dtype : data-type

Data type of the resulting array. If this is a record data-type, the resulting array will be 1-dimensional, and each row will be interpreted as an element of the array. In this case, the number of columns used must match the number of fields in the data-type.

comments : string, optional

The character used to indicate the start of a comment.

delimiter : string, optional

The string used to separate values. By default, this is any whitespace.

converters : {}

A dictionary mapping column number to a function that will convert that column to a float. E.g., if column 0 is a date string: converters = {0: datestr2num}. Converters can also be used to provide a default value for missing data: converters = {3: lambda s: float(s or 0)}.

skiprows : int

Skip the first skiprows lines.

usecols : sequence

Which columns to read, with 0 being the first. For example, usecols = (1,4,5) will extract the 2nd, 5th and 6th columns.

unpack : bool

If True, the returned array is transposed, so that arguments may be unpacked using x, y, z = loadtxt(...)

Returns:

out : ndarray

Data read from the text file.

See also

scipy.io.loadmat

reads Matlab(R) data files

Examples

>>> from StringIO import StringIO   # StringIO behaves like a file object
>>> c = StringIO("0 1\n2 3")
>>> np.loadtxt(c)
array([[ 0.,  1.],
       [ 2.,  3.]])

>>> d = StringIO("M 21 72\nF 35 58")
>>> np.loadtxt(d, dtype={'names': ('gender', 'age', 'weight'),
...                      'formats': ('S1', 'i4', 'f4')})
array([('M', 21, 72.0), ('F', 35, 58.0)],
      dtype=[('gender', '|S1'), ('age', '<i4'), ('weight', '<f4')])

>>> c = StringIO("1,0,2\n3,0,4")
>>> x,y = np.loadtxt(c, delimiter=',', usecols=(0,2), unpack=True)
>>> x
array([ 1.,  3.])
>>> y
array([ 2.,  4.])