PERF: Simplify some of loadtxt's standard converters.

anntzer · anntzer · commit 78af0873bca7 · 2021-08-06T14:13:12.000+02:00
Standard converters only ever get called with str inputs (loadtxt
performs the required decoding); saving a bunch of runtime typechecks
(in `asstr`) results in a 15-20% speedup when loadtxt()ing the
corresponding types.
diff --git a/numpy/lib/npyio.py b/numpy/lib/npyio.py
@@ -747,9 +747,9 @@ def _floatconv(x):
     (np.integer, lambda x: int(float(x))),
     (np.longdouble, np.longdouble),
     (np.floating, _floatconv),
-    (complex, lambda x: complex(asstr(x).replace('+-', '-'))),
-    (np.bytes_, asbytes),
-    (np.unicode_, asunicode),
+    (complex, lambda x: complex(x.replace('+-', '-'))),
+    (np.bytes_, methodcaller('encode', 'latin-1')),
+    (np.unicode_, str),
 ]
 
 
@@ -763,7 +763,7 @@ def _getconv(dtype):
     for base, conv in _CONVERTERS:
         if issubclass(dtype.type, base):
             return conv
-    return asstr
+    return str
 
 
 # _loadtxt_flatten_dtype_internal and _loadtxt_pack_items are loadtxt helpers
