"""
pint.systems
~~~~~~~~~~~~
Functions and classes related to system definitions and conversions.
:copyright: 2016 by Pint Authors, see AUTHORS for more details.
:license: BSD, see LICENSE for more details.
"""
import re
from pint.compat import babel_parse
from .babel_names import _babel_systems
from .definitions import Definition, UnitDefinition
from .errors import DefinitionSyntaxError, RedefinitionError
from .util import (
SharedRegistryObject,
SourceIterator,
getattr_maybe_raise,
logger,
to_units_container,
)
[docs]class Group(SharedRegistryObject):
"""A group is a set of units.
Units can be added directly or by including other groups.
Members are computed dynamically, that is if a unit is added to a group X
all groups that include X are affected.
The group belongs to one Registry.
It can be specified in the definition file as::
@group <name> [using <group 1>, ..., <group N>]
<definition 1>
...
<definition N>
@end
"""
#: Regex to match the header parts of a definition.
_header_re = re.compile(r"@group\s+(?P<name>\w+)\s*(using\s(?P<used_groups>.*))*")
def __init__(self, name):
"""
:param name: Name of the group. If not given, a root Group will be created.
:type name: str
:param groups: dictionary like object groups and system.
The newly created group will be added after creation.
:type groups: dict[str | Group]
"""
# The name of the group.
#: type: str
self.name = name
#: Names of the units in this group.
#: :type: set[str]
self._unit_names = set()
#: Names of the groups in this group.
#: :type: set[str]
self._used_groups = set()
#: Names of the groups in which this group is contained.
#: :type: set[str]
self._used_by = set()
# Add this group to the group dictionary
self._REGISTRY._groups[self.name] = self
if name != "root":
# All groups are added to root group
self._REGISTRY._groups["root"].add_groups(name)
#: A cache of the included units.
#: None indicates that the cache has been invalidated.
#: :type: frozenset[str] | None
self._computed_members = None
@property
def members(self):
"""Names of the units that are members of the group.
Calculated to include to all units in all included _used_groups.
"""
if self._computed_members is None:
self._computed_members = set(self._unit_names)
for _, group in self.iter_used_groups():
self._computed_members |= group.members
self._computed_members = frozenset(self._computed_members)
return self._computed_members
[docs] def invalidate_members(self):
"""Invalidate computed members in this Group and all parent nodes."""
self._computed_members = None
d = self._REGISTRY._groups
for name in self._used_by:
d[name].invalidate_members()
def iter_used_groups(self):
pending = set(self._used_groups)
d = self._REGISTRY._groups
while pending:
name = pending.pop()
group = d[name]
pending |= group._used_groups
yield name, d[name]
def is_used_group(self, group_name):
for name, _ in self.iter_used_groups():
if name == group_name:
return True
return False
[docs] def add_units(self, *unit_names):
"""Add units to group.
"""
for unit_name in unit_names:
self._unit_names.add(unit_name)
self.invalidate_members()
@property
def non_inherited_unit_names(self):
return frozenset(self._unit_names)
[docs] def remove_units(self, *unit_names):
"""Remove units from group.
"""
for unit_name in unit_names:
self._unit_names.remove(unit_name)
self.invalidate_members()
[docs] def add_groups(self, *group_names):
"""Add groups to group.
"""
d = self._REGISTRY._groups
for group_name in group_names:
grp = d[group_name]
if grp.is_used_group(self.name):
raise ValueError(
"Cyclic relationship found between %s and %s"
% (self.name, group_name)
)
self._used_groups.add(group_name)
grp._used_by.add(self.name)
self.invalidate_members()
[docs] def remove_groups(self, *group_names):
"""Remove groups from group.
"""
d = self._REGISTRY._groups
for group_name in group_names:
grp = d[group_name]
self._used_groups.remove(group_name)
grp._used_by.remove(self.name)
self.invalidate_members()
[docs] @classmethod
def from_lines(cls, lines, define_func):
"""Return a Group object parsing an iterable of lines.
Parameters
----------
lines : list[str]
iterable
define_func : callable
Function to define a unit in the registry; it must accept a single string as
a parameter.
Returns
-------
"""
lines = SourceIterator(lines)
lineno, header = next(lines)
r = cls._header_re.search(header)
if r is None:
raise ValueError("Invalid Group header syntax: '%s'" % header)
name = r.groupdict()["name"].strip()
groups = r.groupdict()["used_groups"]
if groups:
group_names = tuple(a.strip() for a in groups.split(","))
else:
group_names = ()
unit_names = []
for lineno, line in lines:
if "=" in line:
# Is a definition
definition = Definition.from_string(line)
if not isinstance(definition, UnitDefinition):
raise DefinitionSyntaxError(
"Only UnitDefinition are valid inside _used_groups, not "
+ str(definition),
lineno=lineno,
)
try:
define_func(definition)
except (RedefinitionError, DefinitionSyntaxError) as ex:
if ex.lineno is None:
ex.lineno = lineno
raise ex
unit_names.append(definition.name)
else:
unit_names.append(line.strip())
grp = cls(name)
grp.add_units(*unit_names)
if group_names:
grp.add_groups(*group_names)
return grp
def __getattr__(self, item):
getattr_maybe_raise(self, item)
return self._REGISTRY
[docs]class System(SharedRegistryObject):
"""A system is a Group plus a set of base units.
Members are computed dynamically, that is if a unit is added to a group X
all groups that include X are affected.
The System belongs to one Registry.
It can be specified in the definition file as::
@system <name> [using <group 1>, ..., <group N>]
<rule 1>
...
<rule N>
@end
The syntax for the rule is:
new_unit_name : old_unit_name
where:
- old_unit_name: a root unit part which is going to be removed from the system.
- new_unit_name: a non root unit which is going to replace the old_unit.
If the new_unit_name and the old_unit_name, the later and the colon can be ommited.
"""
#: Regex to match the header parts of a context.
_header_re = re.compile(r"@system\s+(?P<name>\w+)\s*(using\s(?P<used_groups>.*))*")
def __init__(self, name):
"""
:param name: Name of the group
:type name: str
"""
#: Name of the system
#: :type: str
self.name = name
#: Maps root unit names to a dict indicating the new unit and its exponent.
#: :type: dict[str, dict[str, number]]]
self.base_units = {}
#: Derived unit names.
#: :type: set(str)
self.derived_units = set()
#: Names of the _used_groups in used by this system.
#: :type: set(str)
self._used_groups = set()
#: :type: frozenset | None
self._computed_members = None
# Add this system to the system dictionary
self._REGISTRY._systems[self.name] = self
def __dir__(self):
return list(self.members)
def __getattr__(self, item):
getattr_maybe_raise(self, item)
u = getattr(self._REGISTRY, self.name + "_" + item, None)
if u is not None:
return u
return getattr(self._REGISTRY, item)
@property
def members(self):
d = self._REGISTRY._groups
if self._computed_members is None:
self._computed_members = set()
for group_name in self._used_groups:
try:
self._computed_members |= d[group_name].members
except KeyError:
logger.warning(
"Could not resolve {} in System {}".format(
group_name, self.name
)
)
self._computed_members = frozenset(self._computed_members)
return self._computed_members
[docs] def invalidate_members(self):
"""Invalidate computed members in this Group and all parent nodes."""
self._computed_members = None
[docs] def add_groups(self, *group_names):
"""Add groups to group.
"""
self._used_groups |= set(group_names)
self.invalidate_members()
[docs] def remove_groups(self, *group_names):
"""Remove groups from group.
"""
self._used_groups -= set(group_names)
self.invalidate_members()
@classmethod
def from_lines(cls, lines, get_root_func):
lines = SourceIterator(lines)
lineno, header = next(lines)
r = cls._header_re.search(header)
if r is None:
raise ValueError("Invalid System header syntax '%s'" % header)
name = r.groupdict()["name"].strip()
groups = r.groupdict()["used_groups"]
# If the systems has no group, it automatically uses the root group.
if groups:
group_names = tuple(a.strip() for a in groups.split(","))
else:
group_names = ("root",)
base_unit_names = {}
derived_unit_names = []
for lineno, line in lines:
line = line.strip()
# We would identify a
# - old_unit: a root unit part which is going to be removed from the system.
# - new_unit: a non root unit which is going to replace the old_unit.
if ":" in line:
# The syntax is new_unit:old_unit
new_unit, old_unit = line.split(":")
new_unit, old_unit = new_unit.strip(), old_unit.strip()
# The old unit MUST be a root unit, if not raise an error.
if old_unit != str(get_root_func(old_unit)[1]):
raise ValueError(
"In `%s`, the unit at the right of the `:` must be a root unit."
% line
)
# Here we find new_unit expanded in terms of root_units
new_unit_expanded = to_units_container(get_root_func(new_unit)[1])
# We require that the old unit is present in the new_unit expanded
if old_unit not in new_unit_expanded:
raise ValueError("Old unit must be a component of new unit")
# Here we invert the equation, in other words
# we write old units in terms new unit and expansion
new_unit_dict = {
new_unit: -1.0 / value
for new_unit, value in new_unit_expanded.items()
if new_unit != old_unit
}
new_unit_dict[new_unit] = 1 / new_unit_expanded[old_unit]
base_unit_names[old_unit] = new_unit_dict
else:
# The syntax is new_unit
# old_unit is inferred as the root unit with the same dimensionality.
new_unit = line
old_unit_dict = to_units_container(get_root_func(line)[1])
if len(old_unit_dict) != 1:
raise ValueError(
"The new base must be a root dimension if not discarded unit is specified."
)
old_unit, value = dict(old_unit_dict).popitem()
base_unit_names[old_unit] = {new_unit: 1.0 / value}
system = cls(name)
system.add_groups(*group_names)
system.base_units.update(**base_unit_names)
system.derived_units |= set(derived_unit_names)
return system
class Lister:
def __init__(self, d):
self.d = d
def __dir__(self):
return list(self.d.keys())
def __getattr__(self, item):
getattr_maybe_raise(self, item)
return self.d[item]
_Group = Group
_System = System
def build_group_class(registry):
class Group(_Group):
_REGISTRY = registry
return Group
def build_system_class(registry):
class System(_System):
_REGISTRY = registry
return System
