How to use a dictionary to translate/replace elements of an array? [duplicate]

Answer 1

With brute-force NumPy broadcasting -

idx = np.nonzero(transdict.keys() == abc_array[:,None])[1]
out = np.asarray(transdict.values())[idx]

With np.searchsorted based searching and indexing -

sort_idx = np.argsort(transdict.keys())
idx = np.searchsorted(transdict.keys(),abc_array,sorter = sort_idx)
out = np.asarray(transdict.values())[sort_idx][idx]

Sample run -

In [1]: abc_array = np.array(['B', 'D', 'A', 'B', 'D', 'A', 'C'])
   ...: transdict = {'A': 'Adelaide', 'B': 'Bombay', 'C': 'Cologne', 'D': 'Delhi'}
   ...: 

In [2]: idx = np.nonzero(transdict.keys() == abc_array[:,None])[1]
   ...: out = np.asarray(transdict.values())[idx]
   ...: 

In [3]: out
Out[3]: 
array(['Bombay', 'Delhi', 'Adelaide', 'Bombay', 'Delhi', 'Adelaide',
       'Cologne'], 
      dtype='|S8')

In [4]: sort_idx = np.argsort(transdict.keys())
   ...: idx = np.searchsorted(transdict.keys(),abc_array,sorter = sort_idx)
   ...: out = np.asarray(transdict.values())[sort_idx][idx]
   ...: 

In [5]: out
Out[5]: 
array(['Bombay', 'Delhi', 'Adelaide', 'Bombay', 'Delhi', 'Adelaide',
       'Cologne'], 
      dtype='|S8')