Source code for pint.util

"""
    pint.util
    ~~~~~~~~~

    Miscellaneous functions for pint.

    :copyright: 2016 by Pint Authors, see AUTHORS for more details.
    :license: BSD, see LICENSE for more details.
"""

from __future__ import annotations

import inspect
import logging
import math
import operator
import re
from collections.abc import Mapping
from fractions import Fraction
from functools import lru_cache, partial
from logging import NullHandler
from numbers import Number
from token import NAME, NUMBER
from typing import TYPE_CHECKING, ClassVar, Optional, Type, Union

from .compat import NUMERIC_TYPES, tokenizer
from .errors import DefinitionSyntaxError
from .formatting import format_unit
from .pint_eval import build_eval_tree

if TYPE_CHECKING:
    from pint import Quantity, UnitRegistry

    from ._typing import UnitLike

logger = logging.getLogger(__name__)
logger.addHandler(NullHandler())


[docs]def matrix_to_string( matrix, row_headers=None, col_headers=None, fmtfun=lambda x: str(int(x)) ): """Takes a 2D matrix (as nested list) and returns a string. Parameters ---------- matrix : row_headers : (Default value = None) col_headers : (Default value = None) fmtfun : (Default value = lambda x: str(int(x))) Returns ------- """ ret = [] if col_headers: ret.append(("\t" if row_headers else "") + "\t".join(col_headers)) if row_headers: ret += [ rh + "\t" + "\t".join(fmtfun(f) for f in row) for rh, row in zip(row_headers, matrix) ] else: ret += ["\t".join(fmtfun(f) for f in row) for row in matrix] return "\n".join(ret)
[docs]def transpose(matrix): """Takes a 2D matrix (as nested list) and returns the transposed version. Parameters ---------- matrix : Returns ------- """ return [list(val) for val in zip(*matrix)]
[docs]def column_echelon_form(matrix, ntype=Fraction, transpose_result=False): """Calculates the column echelon form using Gaussian elimination. Parameters ---------- matrix : a 2D matrix as nested list. ntype : the numerical type to use in the calculation. (Default value = Fraction) transpose_result : indicates if the returned matrix should be transposed. (Default value = False) Returns ------- type column echelon form, transformed identity matrix, swapped rows """ lead = 0 M = transpose(matrix) _transpose = transpose if transpose_result else lambda x: x rows, cols = len(M), len(M[0]) new_M = [] for row in M: r = [] for x in row: if isinstance(x, float): x = ntype.from_float(x) else: x = ntype(x) r.append(x) new_M.append(r) M = new_M # M = [[ntype(x) for x in row] for row in M] I = [ # noqa: E741 [ntype(1) if n == nc else ntype(0) for nc in range(rows)] for n in range(rows) ] swapped = [] for r in range(rows): if lead >= cols: return _transpose(M), _transpose(I), swapped i = r while M[i][lead] == 0: i += 1 if i != rows: continue i = r lead += 1 if cols == lead: return _transpose(M), _transpose(I), swapped M[i], M[r] = M[r], M[i] I[i], I[r] = I[r], I[i] swapped.append(i) lv = M[r][lead] M[r] = [mrx / lv for mrx in M[r]] I[r] = [mrx / lv for mrx in I[r]] for i in range(rows): if i == r: continue lv = M[i][lead] M[i] = [iv - lv * rv for rv, iv in zip(M[r], M[i])] I[i] = [iv - lv * rv for rv, iv in zip(I[r], I[i])] lead += 1 return _transpose(M), _transpose(I), swapped
[docs]def pi_theorem(quantities, registry=None): """Builds dimensionless quantities using the Buckingham π theorem Parameters ---------- quantities : dict mapping between variable name and units registry : (Default value = None) Returns ------- type a list of dimensionless quantities expressed as dicts """ # Preprocess input and build the dimensionality Matrix quant = [] dimensions = set() if registry is None: getdim = lambda x: x non_int_type = float else: getdim = registry.get_dimensionality non_int_type = registry.non_int_type for name, value in quantities.items(): if isinstance(value, str): value = ParserHelper.from_string(value, non_int_type=non_int_type) if isinstance(value, dict): dims = getdim(registry.UnitsContainer(value)) elif not hasattr(value, "dimensionality"): dims = getdim(value) else: dims = value.dimensionality if not registry and any(not key.startswith("[") for key in dims): logger.warning( "A non dimension was found and a registry was not provided. " "Assuming that it is a dimension name: {}.".format(dims) ) quant.append((name, dims)) dimensions = dimensions.union(dims.keys()) dimensions = list(dimensions) # Calculate dimensionless quantities M = [ [dimensionality[dimension] for name, dimensionality in quant] for dimension in dimensions ] M, identity, pivot = column_echelon_form(M, transpose_result=False) # Collect results # Make all numbers integers and minimize the number of negative exponents. # Remove zeros results = [] for rowm, rowi in zip(M, identity): if any(el != 0 for el in rowm): continue max_den = max(f.denominator for f in rowi) neg = -1 if sum(f < 0 for f in rowi) > sum(f > 0 for f in rowi) else 1 results.append( dict( (q[0], neg * f.numerator * max_den / f.denominator) for q, f in zip(quant, rowi) if f.numerator != 0 ) ) return results
[docs]def solve_dependencies(dependencies): """Solve a dependency graph. Parameters ---------- dependencies : dependency dictionary. For each key, the value is an iterable indicating its dependencies. Returns ------- type iterator of sets, each containing keys of independents tasks dependent only of the previous tasks in the list. """ while dependencies: # values not in keys (items without dep) t = {i for v in dependencies.values() for i in v} - dependencies.keys() # and keys without value (items without dep) t.update(k for k, v in dependencies.items() if not v) # can be done right away if not t: raise ValueError( "Cyclic dependencies exist among these items: {}".format( ", ".join(repr(x) for x in dependencies.items()) ) ) # and cleaned up dependencies = {k: v - t for k, v in dependencies.items() if v} yield t
def find_shortest_path(graph, start, end, path=None): path = (path or []) + [start] if start == end: return path if start not in graph: return None shortest = None for node in graph[start]: if node not in path: newpath = find_shortest_path(graph, node, end, path) if newpath: if not shortest or len(newpath) < len(shortest): shortest = newpath return shortest def find_connected_nodes(graph, start, visited=None): if start not in graph: return None visited = visited or set() visited.add(start) for node in graph[start]: if node not in visited: find_connected_nodes(graph, node, visited) return visited
[docs]class udict(dict): """Custom dict implementing __missing__.""" def __missing__(self, key): return 0
[docs] def copy(self): return udict(self)
[docs]class UnitsContainer(Mapping): """The UnitsContainer stores the product of units and their respective exponent and implements the corresponding operations. UnitsContainer is a read-only mapping. All operations (even in place ones) Parameters ---------- Returns ------- type """ __slots__ = ("_d", "_hash", "_one", "_non_int_type") def __init__(self, *args, **kwargs) -> None: if args and isinstance(args[0], UnitsContainer): default_non_int_type = args[0]._non_int_type else: default_non_int_type = float self._non_int_type = kwargs.pop("non_int_type", default_non_int_type) if self._non_int_type is float: self._one = 1 else: self._one = self._non_int_type("1") d = udict(*args, **kwargs) self._d = d for key, value in d.items(): if not isinstance(key, str): raise TypeError("key must be a str, not {}".format(type(key))) if not isinstance(value, Number): raise TypeError("value must be a number, not {}".format(type(value))) if not isinstance(value, int) and not isinstance(value, self._non_int_type): d[key] = self._non_int_type(value) self._hash = None def copy(self): return self.__copy__() def add(self, key, value): newval = self._d[key] + value new = self.copy() if newval: new._d[key] = newval else: new._d.pop(key) new._hash = None return new
[docs] def remove(self, keys): """Create a new UnitsContainer purged from given keys. Parameters ---------- keys : Returns ------- """ new = self.copy() for k in keys: new._d.pop(k) new._hash = None return new
[docs] def rename(self, oldkey, newkey): """Create a new UnitsContainer in which an entry has been renamed. Parameters ---------- oldkey : newkey : Returns ------- """ new = self.copy() new._d[newkey] = new._d.pop(oldkey) new._hash = None return new
def __iter__(self): return iter(self._d) def __len__(self) -> int: return len(self._d) def __getitem__(self, key): return self._d[key] def __contains__(self, key): return key in self._d def __hash__(self): if self._hash is None: self._hash = hash(frozenset(self._d.items())) return self._hash # Only needed by pickle protocol 0 and 1 (used by pytables) def __getstate__(self): return self._d, self._one, self._non_int_type def __setstate__(self, state): self._d, self._one, self._non_int_type = state self._hash = None def __eq__(self, other) -> bool: if isinstance(other, UnitsContainer): # UnitsContainer.__hash__(self) is not the same as hash(self); see # ParserHelper.__hash__ and __eq__. # Different hashes guarantee that the actual contents are different, but # identical hashes give no guarantee of equality. # e.g. in CPython, hash(-1) == hash(-2) if UnitsContainer.__hash__(self) != UnitsContainer.__hash__(other): return False other = other._d elif isinstance(other, str): try: other = ParserHelper.from_string(other, self._non_int_type) except DefinitionSyntaxError: return False other = other._d return dict.__eq__(self._d, other) def __str__(self) -> str: return self.__format__("") def __repr__(self) -> str: tmp = "{%s}" % ", ".join( ["'{}': {}".format(key, value) for key, value in sorted(self._d.items())] ) return "<UnitsContainer({})>".format(tmp) def __format__(self, spec: str) -> str: return format_unit(self, spec) def format_babel(self, spec: str, registry=None, **kwspec) -> str: return format_unit(self, spec, registry=registry, **kwspec) def __copy__(self): # Skip expensive health checks performed by __init__ out = object.__new__(self.__class__) out._d = self._d.copy() out._hash = self._hash out._non_int_type = self._non_int_type out._one = self._one return out def __mul__(self, other): if not isinstance(other, self.__class__): err = "Cannot multiply UnitsContainer by {}" raise TypeError(err.format(type(other))) new = self.copy() for key, value in other.items(): new._d[key] += value if new._d[key] == 0: del new._d[key] new._hash = None return new __rmul__ = __mul__ def __pow__(self, other): if not isinstance(other, NUMERIC_TYPES): err = "Cannot power UnitsContainer by {}" raise TypeError(err.format(type(other))) new = self.copy() for key, value in new._d.items(): new._d[key] *= other new._hash = None return new def __truediv__(self, other): if not isinstance(other, self.__class__): err = "Cannot divide UnitsContainer by {}" raise TypeError(err.format(type(other))) new = self.copy() for key, value in other.items(): new._d[key] -= value if new._d[key] == 0: del new._d[key] new._hash = None return new def __rtruediv__(self, other): if not isinstance(other, self.__class__) and other != 1: err = "Cannot divide {} by UnitsContainer" raise TypeError(err.format(type(other))) return self**-1
[docs]class ParserHelper(UnitsContainer): """The ParserHelper stores in place the product of variables and their respective exponent and implements the corresponding operations. ParserHelper is a read-only mapping. All operations (even in place ones) Parameters ---------- Returns ------- type WARNING : The hash value used does not take into account the scale attribute so be careful if you use it as a dict key and then two unequal object can have the same hash. """ __slots__ = ("scale",) def __init__(self, scale=1, *args, **kwargs): super().__init__(*args, **kwargs) self.scale = scale
[docs] @classmethod def from_word(cls, input_word, non_int_type=float): """Creates a ParserHelper object with a single variable with exponent one. Equivalent to: ParserHelper({'word': 1}) Parameters ---------- input_word : Returns ------- """ if non_int_type is float: return cls(1, [(input_word, 1)], non_int_type=non_int_type) else: ONE = non_int_type("1.0") return cls(ONE, [(input_word, ONE)], non_int_type=non_int_type)
@classmethod def eval_token(cls, token, use_decimal=False, non_int_type=float): # TODO: remove this code when use_decimal is deprecated if use_decimal: raise DeprecationWarning( "`use_decimal` is deprecated, use `non_int_type` keyword argument when instantiating the registry.\n" ">>> from decimal import Decimal\n" ">>> ureg = UnitRegistry(non_int_type=Decimal)" ) token_type = token.type token_text = token.string if token_type == NUMBER: if non_int_type is float: try: return int(token_text) except ValueError: return float(token_text) else: return non_int_type(token_text) elif token_type == NAME: return ParserHelper.from_word(token_text, non_int_type=non_int_type) else: raise Exception("unknown token type")
[docs] @classmethod @lru_cache() def from_string(cls, input_string, non_int_type=float): """Parse linear expression mathematical units and return a quantity object. Parameters ---------- input_string : Returns ------- """ if not input_string: return cls(non_int_type=non_int_type) input_string = string_preprocessor(input_string) if "[" in input_string: input_string = input_string.replace("[", "__obra__").replace( "]", "__cbra__" ) reps = True else: reps = False gen = tokenizer(input_string) ret = build_eval_tree(gen).evaluate( partial(cls.eval_token, non_int_type=non_int_type) ) if isinstance(ret, Number): return cls(ret, non_int_type=non_int_type) if reps: ret = cls( ret.scale, { key.replace("__obra__", "[").replace("__cbra__", "]"): value for key, value in ret.items() }, non_int_type=non_int_type, ) for k in list(ret): if k.lower() == "nan": del ret._d[k] ret.scale = math.nan return ret
def __copy__(self): new = super().__copy__() new.scale = self.scale return new def copy(self): return self.__copy__() def __hash__(self): if self.scale != 1: mess = "Only scale 1 ParserHelper instance should be considered hashable" raise ValueError(mess) return super().__hash__() # Only needed by pickle protocol 0 and 1 (used by pytables) def __getstate__(self): return super().__getstate__() + (self.scale,) def __setstate__(self, state): super().__setstate__(state[:-1]) self.scale = state[-1] def __eq__(self, other): if isinstance(other, ParserHelper): return self.scale == other.scale and super().__eq__(other) elif isinstance(other, str): return self == ParserHelper.from_string(other, self._non_int_type) elif isinstance(other, Number): return self.scale == other and not len(self._d) else: return self.scale == 1 and super().__eq__(other) def operate(self, items, op=operator.iadd, cleanup=True): d = udict(self._d) for key, value in items: d[key] = op(d[key], value) if cleanup: keys = [key for key, value in d.items() if value == 0] for key in keys: del d[key] return self.__class__(self.scale, d, non_int_type=self._non_int_type) def __str__(self): tmp = "{%s}" % ", ".join( ["'{}': {}".format(key, value) for key, value in sorted(self._d.items())] ) return "{} {}".format(self.scale, tmp) def __repr__(self): tmp = "{%s}" % ", ".join( ["'{}': {}".format(key, value) for key, value in sorted(self._d.items())] ) return "<ParserHelper({}, {})>".format(self.scale, tmp) def __mul__(self, other): if isinstance(other, str): new = self.add(other, self._one) elif isinstance(other, Number): new = self.copy() new.scale *= other elif isinstance(other, self.__class__): new = self.operate(other.items()) new.scale *= other.scale else: new = self.operate(other.items()) return new __rmul__ = __mul__ def __pow__(self, other): d = self._d.copy() for key in self._d: d[key] *= other return self.__class__(self.scale**other, d, non_int_type=self._non_int_type) def __truediv__(self, other): if isinstance(other, str): new = self.add(other, -1) elif isinstance(other, Number): new = self.copy() new.scale /= other elif isinstance(other, self.__class__): new = self.operate(other.items(), operator.sub) new.scale /= other.scale else: new = self.operate(other.items(), operator.sub) return new __floordiv__ = __truediv__ def __rtruediv__(self, other): new = self.__pow__(-1) if isinstance(other, str): new = new.add(other, self._one) elif isinstance(other, Number): new.scale *= other elif isinstance(other, self.__class__): new = self.operate(other.items(), operator.add) new.scale *= other.scale else: new = new.operate(other.items(), operator.add) return new
#: List of regex substitution pairs. _subs_re_list = [ ("\N{DEGREE SIGN}", " degree"), (r"([\w\.\-\+\*\\\^])\s+", r"\1 "), # merge multiple spaces (r"({}) squared", r"\1**2"), # Handle square and cube (r"({}) cubed", r"\1**3"), (r"cubic ({})", r"\1**3"), (r"square ({})", r"\1**2"), (r"sq ({})", r"\1**2"), ( r"\b([0-9]+\.?[0-9]*)(?=[e|E][a-zA-Z]|[a-df-zA-DF-Z])", r"\1*", ), # Handle numberLetter for multiplication (r"([\w\.\-])\s+(?=\w)", r"\1*"), # Handle space for multiplication ] #: Compiles the regex and replace {} by a regex that matches an identifier. _subs_re = [ (re.compile(a.format(r"[_a-zA-Z][_a-zA-Z0-9]*")), b) for a, b in _subs_re_list ] _pretty_table = str.maketrans("⁰¹²³⁴⁵⁶⁷⁸⁹·⁻", "0123456789*-") _pretty_exp_re = re.compile(r"(⁻?[⁰¹²³⁴⁵⁶⁷⁸⁹]+(?:\.[⁰¹²³⁴⁵⁶⁷⁸⁹]*)?)") def string_preprocessor(input_string: str) -> str: input_string = input_string.replace(",", "") input_string = input_string.replace(" per ", "/") for a, b in _subs_re: input_string = a.sub(b, input_string) input_string = _pretty_exp_re.sub(r"**(\1)", input_string) # Replace pretty format characters input_string = input_string.translate(_pretty_table) # Handle caret exponentiation input_string = input_string.replace("^", "**") return input_string def _is_dim(name: str) -> bool: return name[0] == "[" and name[-1] == "]"
[docs]class SharedRegistryObject: """Base class for object keeping a reference to the registree. Such object are for now Quantity and Unit, in a number of places it is that an object from this class has a '_units' attribute. Parameters ---------- Returns ------- """ _REGISTRY: ClassVar[UnitRegistry] _units: UnitsContainer def __new__(cls, *args, **kwargs): inst = object.__new__(cls) if not hasattr(cls, "_REGISTRY"): # Base class, not subclasses dynamically by # UnitRegistry._init_dynamic_classes from . import application_registry inst._REGISTRY = application_registry.get() return inst def _check(self, other) -> bool: """Check if the other object use a registry and if so that it is the same registry. Parameters ---------- other : Returns ------- type other don't use a registry and raise ValueError if other don't use the same unit registry. """ if self._REGISTRY is getattr(other, "_REGISTRY", None): return True elif isinstance(other, SharedRegistryObject): mess = "Cannot operate with {} and {} of different registries." raise ValueError( mess.format(self.__class__.__name__, other.__class__.__name__) ) else: return False
[docs]class PrettyIPython: """Mixin to add pretty-printers for IPython""" default_format: str def _repr_html_(self): if "~" in self.default_format: return "{:~H}".format(self) else: return "{:H}".format(self) def _repr_latex_(self): if "~" in self.default_format: return "${:~L}$".format(self) else: return "${:L}$".format(self) def _repr_pretty_(self, p, cycle): if "~" in self.default_format: p.text("{:~P}".format(self)) else: p.text("{:P}".format(self))
[docs]def to_units_container( unit_like: Union[UnitLike, Quantity], registry: Optional[UnitRegistry] = None ) -> UnitsContainer: """Convert a unit compatible type to a UnitsContainer. Parameters ---------- unit_like : registry : (Default value = None) Returns ------- """ mro = type(unit_like).mro() if UnitsContainer in mro: return unit_like elif SharedRegistryObject in mro: return unit_like._units elif str in mro: if registry: return registry._parse_units(unit_like) else: return ParserHelper.from_string(unit_like) elif dict in mro: if registry: return registry.UnitsContainer(unit_like) else: return UnitsContainer(unit_like)
[docs]def infer_base_unit( unit_like: Union[UnitLike, Quantity], registry: Optional[UnitRegistry] = None ) -> UnitsContainer: """ Given a Quantity or UnitLike, give the UnitsContainer for it's plain units. Parameters ---------- unit_like : Union[UnitLike, Quantity] Quantity or Unit to infer the plain units from. registry: Optional[UnitRegistry] If provided, uses the registry's UnitsContainer and parse_unit_name. If None, uses the registry attached to unit_like. Returns ------- UnitsContainer Raises ------ ValueError The unit_like did not reference a registry, and no registry was provided. """ d = udict() original_units = to_units_container(unit_like, registry) if registry is None and hasattr(unit_like, "_REGISTRY"): registry = unit_like._REGISTRY if registry is None: raise ValueError("No registry provided.") for unit_name, power in original_units.items(): candidates = registry.parse_unit_name(unit_name) assert len(candidates) == 1 _, base_unit, _ = candidates[0] d[base_unit] += power # remove values that resulted in a power of 0 nonzero_dict = {k: v for k, v in d.items() if v != 0} return registry.UnitsContainer(nonzero_dict)
[docs]def getattr_maybe_raise(self, item): """Helper function invoked at start of all overridden ``__getattr__``. Raise AttributeError if the user tries to ask for a _ or __ attribute, *unless* it is immediately followed by a number, to enable units encompassing constants, such as ``L / _100km``. Parameters ---------- item : string Item to be found. Returns ------- """ # Double-underscore attributes are tricky to detect because they are # automatically prefixed with the class name - which may be a subclass of self if ( item.endswith("__") or len(item.lstrip("_")) == 0 or (item.startswith("_") and not item.lstrip("_")[0].isdigit()) ): raise AttributeError("%r object has no attribute %r" % (self, item))
[docs]class SourceIterator: """Iterator to facilitate reading the definition files. Accepts any sequence (like a list of lines, a file or another SourceIterator) The iterator yields the line number and line (skipping comments and empty lines) and stripping white spaces. for lineno, line in SourceIterator(sequence): # do something here """ def __new__(cls, sequence, filename=None, is_resource=False): if isinstance(sequence, SourceIterator): return sequence obj = object.__new__(cls) if sequence is not None: obj.internal = enumerate(sequence, 1) obj.last = (None, None) obj.filename = filename or getattr(sequence, "name", None) obj.is_resource = is_resource return obj def __iter__(self): return self def __next__(self): line = "" while not line or line.startswith("#"): lineno, line = next(self.internal) line = line.split("#", 1)[0].strip() self.last = lineno, line return lineno, line next = __next__
[docs] def block_iter(self): """Iterate block including header.""" return BlockIterator(self)
[docs]class BlockIterator(SourceIterator): """Like SourceIterator but stops when it finds '@end' It also raises an error if another '@' directive is found inside. """ def __new__(cls, line_iterator): obj = SourceIterator.__new__(cls, None) obj.internal = line_iterator.internal obj.last = line_iterator.last obj.done_last = False return obj def __next__(self): if not self.done_last: self.done_last = True return self.last lineno, line = SourceIterator.__next__(self) if line.startswith("@end"): raise StopIteration elif line.startswith("@"): raise DefinitionSyntaxError("cannot nest @ directives", lineno=lineno) return lineno, line next = __next__
[docs]def iterable(y) -> bool: """Check whether or not an object can be iterated over. Vendored from numpy under the terms of the BSD 3-Clause License. (Copyright (c) 2005-2019, NumPy Developers.) Parameters ---------- value : Input object. type : object y : """ try: iter(y) except TypeError: return False return True
[docs]def sized(y) -> bool: """Check whether or not an object has a defined length. Parameters ---------- value : Input object. type : object y : """ try: len(y) except TypeError: return False return True
[docs]def build_dependent_class(registry_class, class_name: str, attribute_name: str) -> Type: """Creates a class specifically for the given registry that subclass all the classes named by the registry bases in a specific attribute 1. List the 'attribute_name' attribute for each of the bases of the registry class. 2. Use this list as bases for the new class 3. Add the provided registry as the class registry. """ bases = ( getattr(base, attribute_name) for base in inspect.getmro(registry_class) if attribute_name in base.__dict__ ) bases = dict.fromkeys(bases, None) newcls = type(class_name, tuple(bases.keys()), dict()) return newcls
[docs]def create_class_with_registry(registry, base_class) -> Type: """Create new class inheriting from base_class and filling _REGISTRY class attribute with an actual instanced registry. """ return type(base_class.__name__, tuple((base_class,)), dict(_REGISTRY=registry))