numpy.fromfile(file, dtype=float, count=-1, sep='')

Construct an array from data in a text or binary file.

A highly efficient way of reading binary data with a known data-type, as well as parsing simply formatted text files. Data written using the tofile method can be read using this function.

file : file or str

Open file object or filename.

dtype : data-type

Data type of the returned array. For binary files, it is used to determine the size and byte-order of the items in the file.

count : int

Number of items to read. -1 means all items (i.e., the complete file).

sep : str

Separator between items if file is a text file. Empty (“”) separator means the file should be treated as binary. Spaces (” “) in the separator match zero or more whitespace characters. A separator consisting only of spaces must match at least one whitespace.

See also

load, save, ndarray.tofile

More flexible way of loading data from a text file.


Do not rely on the combination of tofile and fromfile for data storage, as the binary files generated are are not platform independent. In particular, no byte-order or data-type information is saved. Data can be stored in the platform independent .npy format using save and load instead.


Construct an ndarray:

>>> dt = np.dtype([('time', [('min', int), ('sec', int)]),
...                ('temp', float)])
>>> x = np.zeros((1,), dtype=dt)
>>> x['time']['min'] = 10; x['temp'] = 98.25
>>> x
array([((10, 0), 98.25)],
      dtype=[('time', [('min', '<i4'), ('sec', '<i4')]), ('temp', '<f8')])

Save the raw data to disk:

>>> import os
>>> fname = os.tmpnam()
>>> x.tofile(fname)

Read the raw data from disk:

>>> np.fromfile(fname, dtype=dt)
array([((10, 0), 98.25)],
      dtype=[('time', [('min', '<i4'), ('sec', '<i4')]), ('temp', '<f8')])

The recommended way to store and load data:

>>>, x)
>>> np.load(fname + '.npy')
array([((10, 0), 98.25)],
      dtype=[('time', [('min', '<i4'), ('sec', '<i4')]), ('temp', '<f8')])

Previous topic


Next topic