NumPy Input and Output: ndarray.tofile() function

Last update on August 19 2022 21:51:10 (UTC/GMT +8 hours)

numpy.ndarray.tofile() function

The ndarray.tofile() function is used to write array to a file as text or binary (default).

Data is always written in 'C' order, independent of the order of a.

Syntax:

ndarray.tofile(fid, sep="", format="%s")

Version: 1.15.0

Parameter:

Name	Description	Required / Optional
fid	An open file object, or a string containing a filename. file or str	Required
sep	Separator between array items for text output. If "" (empty), a binary file is written, equivalent to file.write(a.tobytes()). str	Required
format	Format string for text file output. Each entry in the array is formatted to text by first converting it to the closest Python type, and then using "format" % item. str	Required

Notes:
This is a convenience function for quick storage of array data.
Information on endianness and precision is lost, so this method is not a good choice for files intended to archive data or transport data between machines with different endianness.
Some of these problems can be overcome by outputting the data as text files, at the expense of speed and file size.

When fid is a file object, array contents are directly written to the file, bypassing the file object's write method.
As a result, tofile cannot be used with files objects supporting compression (e.g., GzipFile) or file-like objects that do not support fileno() (e.g., BytesIO).

NumPy.fromstring() method Example:

>>> import numpy as np
>>> np.array([1,300],np.int32).tofile('test1')
>>> with open('test1','rb') as x: print(x.read())

Output:

 b'\x01\x00\x00\x00,\x01\x00\x00'

Python - NumPy Code Editor:

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