numpy.fliplr
Flip array in the left/right direction.

ValueError: Input must be >= 2-d.

https://ideone.com/xd3w1U (Python 3.5)

import numpy as np

xs = [[3, 1, 4], [1, 5, 9]]
res = np.fliplr(xs)
print(res)

xs = [3, 1, 4]
res = np.fliplr(xs)
print(res)

run

[[4 1 3]
 [9 5 1]]

stderr

Traceback (most recent call last):
  File "./prog.py", line 4, in <module>
  File "/usr/lib/python3/dist-packages/numpy/lib/twodim_base.py", line 81, in fliplr
    raise ValueError("Input must be >= 2-d.")
ValueError: Input must be >= 2-d.

エラーの詳細

153行あたり

    if m.ndim < 2:
        raise ValueError, "Input must >= 2-d."

このエラーが出ているようだ。