diff options
Diffstat (limited to 'numpy/lib/recfunctions.py')
| -rw-r--r-- | numpy/lib/recfunctions.py | 40 |
1 files changed, 35 insertions, 5 deletions
diff --git a/numpy/lib/recfunctions.py b/numpy/lib/recfunctions.py index d3d58d1f2..b9542e848 100644 --- a/numpy/lib/recfunctions.py +++ b/numpy/lib/recfunctions.py @@ -495,7 +495,7 @@ def drop_fields(base, drop_names, usemask=True, asrecarray=False): dtype=[('a', '<i4')]) """ if _is_string_like(drop_names): - drop_names = [drop_names, ] + drop_names = [drop_names] else: drop_names = set(drop_names) @@ -523,6 +523,31 @@ def drop_fields(base, drop_names, usemask=True, asrecarray=False): return _fix_output(output, usemask=usemask, asrecarray=asrecarray) +def _keep_fields(base, keep_names, usemask=True, asrecarray=False): + """ + Return a new array keeping only the fields in `keep_names`, + and preserving the order of those fields. + + Parameters + ---------- + base : array + Input array + keep_names : string or sequence + String or sequence of strings corresponding to the names of the + fields to keep. Order of the names will be preserved. + usemask : {False, True}, optional + Whether to return a masked array or not. + asrecarray : string or sequence, optional + Whether to return a recarray or a mrecarray (`asrecarray=True`) or + a plain ndarray or masked array with flexible dtype. The default + is False. + """ + newdtype = [(n, base.dtype[n]) for n in keep_names] + output = np.empty(base.shape, dtype=newdtype) + output = recursive_fill_fields(base, output) + return _fix_output(output, usemask=usemask, asrecarray=asrecarray) + + def rec_drop_fields(base, drop_names): """ Returns a new numpy.recarray with fields in `drop_names` dropped. @@ -877,11 +902,14 @@ def join_by(key, r1, r2, jointype='inner', r1postfix='1', r2postfix='2', key = (key,) # Check the keys + if len(set(key)) != len(key): + dup = next(x for n,x in enumerate(key) if x in key[n+1:]) + raise ValueError("duplicate join key %r" % dup) for name in key: if name not in r1.dtype.names: - raise ValueError('r1 does not have key field %s' % name) + raise ValueError('r1 does not have key field %r' % name) if name not in r2.dtype.names: - raise ValueError('r2 does not have key field %s' % name) + raise ValueError('r2 does not have key field %r' % name) # Make sure we work with ravelled arrays r1 = r1.ravel() @@ -899,8 +927,10 @@ def join_by(key, r1, r2, jointype='inner', r1postfix='1', r2postfix='2', raise ValueError(msg) # Make temporary arrays of just the keys - r1k = drop_fields(r1, [n for n in r1names if n not in key]) - r2k = drop_fields(r2, [n for n in r2names if n not in key]) + # (use order of keys in `r1` for back-compatibility) + key1 = [ n for n in r1names if n in key ] + r1k = _keep_fields(r1, key1) + r2k = _keep_fields(r2, key1) # Concatenate the two arrays for comparison aux = ma.concatenate((r1k, r2k)) |