CODEWITHSUNDEEP
pythonarraysnumpy
Gabriel
Gabriel

Reputation: 42349

Append array to beginning of another array

I'm attempting to perform a simple task: append an array to the beginning of another array. Here a MWE of what I mean:

a = ['a','b','c','d','e','f','g','h','i']
b = [6,4,1.,2,8,784.,43,6.,2]
c = [8,4.,32.,6,1,7,2.,9,23]

# Define arrays.
a_arr = np.array(a)
bc_arr = np.array([b, c])

# Append a_arr to beginning of bc_arr
print np.concatenate((a_arr, bc_arr), axis=1)

but I keep getting a ValueError: all the input arrays must have same number of dimensions error.

The arrays a_arr and bc_arr come like that from a different process so I can't manipulate the way they are created (ie: I can't use the a,b,c lists).

How can I generate a new array of a_arr and bc_arr so that it will look like:

array(['a','b','c','d','e','f','g','h','i'], [6,4,1.,2,8,784.,43,6.,2], [8,4.,32.,6,1,7,2.,9,23])

Upvotes: 0

Views: 295

Answers (2)

Padraic Cunningham
Padraic Cunningham

Reputation: 180441

Can you do something like.

In [88]: a = ['a','b','c','d','e','f','g','h','i']

In [89]: b = [6,4,1.,2,8,784.,43,6.,2]

In [90]: c = [8,4.,32.,6,1,7,2.,9,23]

In [91]: joined_arr=np.array([a_arr,b_arr,c_arr],dtype=object)

In [92]: joined_arr
Out[92]: 
array([['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i'],
       [6.0, 4.0, 1.0, 2.0, 8.0, 784.0, 43.0, 6.0, 2.0],
       [8.0, 4.0, 32.0, 6.0, 1.0, 7.0, 2.0, 9.0, 23.0]], dtype=object)

Upvotes: 1

Moj
Moj

Reputation: 6361

this should work

In [84]: a=np.atleast_2d(a).astype('object')

In [85]: b=np.atleast_2d(b).astype('object')

In [86]: c=np.atleast_2d(c).astype('object')

In [87]: np.vstack((a,b,c))
Out[87]:
array([[a, b, c, d, e, f, g, h, i],
       [6.0, 4.0, 1.0, 2.0, 8.0, 784.0, 43.0, 6.0, 2.0],
       [8.0, 4.0, 32.0, 6.0, 1.0, 7.0, 2.0, 9.0, 23.0]], dtype=object)

Upvotes: 1

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