I have a matrix of strings. How do I add a column to the front, like
[['a','b'], ==> [['e','a','b'],
['c','d'], ['e','c','d'],
['a','b'], ==> ['e','a','b'],
['c','d'], ['e','c','d'],
['a','b'], ==> ['e','a','b'],
['c','d']] ['e','c','d']]
The answer in @Paul's comments explains it all. Adding here for completeness.
In [1]: a = np.tile(np.array([["a","b"], ["c","d"]]), (3,1))
In [2]: a
Out[2]: array([['a', 'b'],
['c', 'd'],
['a', 'b'],
['c', 'd'],
['a', 'b'],
['c', 'd']],
dtype='<U1')
In [3]: e = np.tile("e", a.shape[0])[None].T # REF: https://stackoverflow.com/a/11885718/155813
In [4]: e
Out[4]: array([['e'],
['e'],
['e'],
['e'],
['e'],
['e']],
dtype='<U1')
In [5]: np.hstack([e, a])
Out[5]: array([['e', 'a', 'b'],
['e', 'c', 'd'],
['e', 'a', 'b'],
['e', 'c', 'd'],
['e', 'a', 'b'],
['e', 'c', 'd']],
dtype='<U1')
es