Simple way of creating a 2D array with random numbers (Python) -

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i know easy way create nxn array full of zeroes in python with:

[[0]*n x in range(n)]

however, let's suppose want create array filling random numbers:

[[random.random()]*n x in range(n)]

this doesn't work because each random number created replicated n times, array doesn't have nxn unique random numbers.

is there way of doing in single line, without using loops?

you use nested list comprehension:

>>> n = 5 >>> import random >>> [[random.random() in range(n)] j in range(n)] [[0.9520388778975947, 0.29456222450756675, 0.33025941906885714, 0.6154639550493386, 0.11409250305307261], [0.6149070141685593, 0.3579148659939374, 0.031188652624532298, 0.4607597656919963, 0.2523207155544883], [0.6372935479559158, 0.32063181293207754, 0.700897108426278, 0.822287873035571, 0.7721460935656276], [0.31035121801363097, 0.2691153671697625, 0.1185063432179293, 0.14822226436085928, 0.5490604341460457], [0.9650509333411779, 0.7795665950184245, 0.5778752066273084, 0.3868760955504583, 0.5364495147637446]]

or use numpy (non-stdlib popular):

>>> import numpy np >>> np.random.random((n,n)) array([[ 0.26045197,  0.66184973,  0.79957904,  0.82613958,  0.39644677],        [ 0.09284838,  0.59098542,  0.13045167,  0.06170584,  0.01265676],        [ 0.16456109,  0.87820099,  0.79891448,  0.02966868,  0.27810629],        [ 0.03037986,  0.31481138,  0.06477025,  0.37205248,  0.59648463],        [ 0.08084797,  0.10305354,  0.72488268,  0.30258304,  0.230913  ]])

(p.s. it's idea in habit of saying list when mean list , reserving array numpy ndarrays. there's built-in array module own array type, confuses things more, it's relatively seldom used.)


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