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Reading and Writing Ndarrays

The NumPy package offers several functions for reading and writing ndarrays:

import numpy as np
import os
# Example: the save and load functions
m = np.array([[1, 2, 3], [4, 5, 6]])
file_name = "matrix.npy"
np.save(file_name, m)
print("File Size in Bytes:", os.stat(file_name).st_size)
loaded = np.load(file_name)
# Example: the savez and savez_compressed functions
file_name = "output.npz"
for save in np.savez, np.savez_compressed:
save(file_name, foo=np.array([1, 2]), bar=np.array([3, 4]))
arrays = np.load(file_name)
print("Using {}, {} bytes:".format(
for key, value in arrays.items(): # unordered
print("\t{}: {}".format(key, value))
print() # empty line
# Example: the savetxt and loadtxt functions
def print_file(file_name):
with open(file_name) as f:
for line in f:
print(line, end='')
file_name = "array.txt"
np.savetxt(file_name, np.array([[1, 3], [2, 4]]))
loaded = np.loadtxt(file_name)
print("Using numpy.loadtxt:\n{}".format(loaded))
print("Text File Content:")
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