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Mini Shell
#!/usr/bin/env python3
"""Prints type-coercion tables for the built-in NumPy types
"""
import numpy as np
from collections import namedtuple
# Generic object that can be added, but doesn't do anything else
class GenericObject:
def __init__(self, v):
self.v = v
def __add__(self, other):
return self
def __radd__(self, other):
return self
dtype = np.dtype('O')
def print_cancast_table(ntypes):
print('X', end=' ')
for char in ntypes:
print(char, end=' ')
print()
for row in ntypes:
print(row, end=' ')
for col in ntypes:
if np.can_cast(row, col, "equiv"):
cast = "#"
elif np.can_cast(row, col, "safe"):
cast = "="
elif np.can_cast(row, col, "same_kind"):
cast = "~"
elif np.can_cast(row, col, "unsafe"):
cast = "."
else:
cast = " "
print(cast, end=' ')
print()
def print_coercion_table(ntypes, inputfirstvalue, inputsecondvalue, firstarray, use_promote_types=False):
print('+', end=' ')
for char in ntypes:
print(char, end=' ')
print()
for row in ntypes:
if row == 'O':
rowtype = GenericObject
else:
rowtype = np.obj2sctype(row)
print(row, end=' ')
for col in ntypes:
if col == 'O':
coltype = GenericObject
else:
coltype = np.obj2sctype(col)
try:
if firstarray:
rowvalue = np.array([rowtype(inputfirstvalue)], dtype=rowtype)
else:
rowvalue = rowtype(inputfirstvalue)
colvalue = coltype(inputsecondvalue)
if use_promote_types:
char = np.promote_types(rowvalue.dtype, colvalue.dtype).char
else:
value = np.add(rowvalue, colvalue)
if isinstance(value, np.ndarray):
char = value.dtype.char
else:
char = np.dtype(type(value)).char
except ValueError:
char = '!'
except OverflowError:
char = '@'
except TypeError:
char = '#'
print(char, end=' ')
print()
def print_new_cast_table(*, can_cast=True, legacy=False, flags=False):
"""Prints new casts, the values given are default "can-cast" values, not
actual ones.
"""
from numpy.core._multiarray_tests import get_all_cast_information
cast_table = {
-1: " ",
0: "#", # No cast (classify as equivalent here)
1: "#", # equivalent casting
2: "=", # safe casting
3: "~", # same-kind casting
4: ".", # unsafe casting
}
flags_table = {
0 : "▗", 7: "█",
1: "▚", 2: "▐", 4: "▄",
3: "▜", 5: "▙",
6: "▟",
}
cast_info = namedtuple("cast_info", ["can_cast", "legacy", "flags"])
no_cast_info = cast_info(" ", " ", " ")
casts = get_all_cast_information()
table = {}
dtypes = set()
for cast in casts:
dtypes.add(cast["from"])
dtypes.add(cast["to"])
if cast["from"] not in table:
table[cast["from"]] = {}
to_dict = table[cast["from"]]
can_cast = cast_table[cast["casting"]]
legacy = "L" if cast["legacy"] else "."
flags = 0
if cast["requires_pyapi"]:
flags |= 1
if cast["supports_unaligned"]:
flags |= 2
if cast["no_floatingpoint_errors"]:
flags |= 4
flags = flags_table[flags]
to_dict[cast["to"]] = cast_info(can_cast=can_cast, legacy=legacy, flags=flags)
# The np.dtype(x.type) is a bit strange, because dtype classes do
# not expose much yet.
types = np.typecodes["All"]
def sorter(x):
# This is a bit weird hack, to get a table as close as possible to
# the one printing all typecodes (but expecting user-dtypes).
dtype = np.dtype(x.type)
try:
indx = types.index(dtype.char)
except ValueError:
indx = np.inf
return (indx, dtype.char)
dtypes = sorted(dtypes, key=sorter)
def print_table(field="can_cast"):
print('X', end=' ')
for dt in dtypes:
print(np.dtype(dt.type).char, end=' ')
print()
for from_dt in dtypes:
print(np.dtype(from_dt.type).char, end=' ')
row = table.get(from_dt, {})
for to_dt in dtypes:
print(getattr(row.get(to_dt, no_cast_info), field), end=' ')
print()
if can_cast:
# Print the actual table:
print()
print("Casting: # is equivalent, = is safe, ~ is same-kind, and . is unsafe")
print()
print_table("can_cast")
if legacy:
print()
print("L denotes a legacy cast . a non-legacy one.")
print()
print_table("legacy")
if flags:
print()
print(f"{flags_table[0]}: no flags, {flags_table[1]}: PyAPI, "
f"{flags_table[2]}: supports unaligned, {flags_table[4]}: no-float-errors")
print()
print_table("flags")
if __name__ == '__main__':
print("can cast")
print_cancast_table(np.typecodes['All'])
print()
print("In these tables, ValueError is '!', OverflowError is '@', TypeError is '#'")
print()
print("scalar + scalar")
print_coercion_table(np.typecodes['All'], 0, 0, False)
print()
print("scalar + neg scalar")
print_coercion_table(np.typecodes['All'], 0, -1, False)
print()
print("array + scalar")
print_coercion_table(np.typecodes['All'], 0, 0, True)
print()
print("array + neg scalar")
print_coercion_table(np.typecodes['All'], 0, -1, True)
print()
print("promote_types")
print_coercion_table(np.typecodes['All'], 0, 0, False, True)
print("New casting type promotion:")
print_new_cast_table(can_cast=True, legacy=True, flags=True)
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