物理量

物理量。

class sympy.physics.units.quantities.Quantity(name, abbrev=None, latex_repr=None, pretty_unicode_repr=None, pretty_ascii_repr=None, mathml_presentation_repr=None, is_prefixed=False, **assumptions)

物理量：可以是度量单位，常量或通用量。

property abbrev

表示单元名称的符号。

如果已定义，则在缩写前面加上前缀符号。

convert_to(other, unit_system='SI')

将该数量转换为另一个相同尺寸的数量。

实例

>>> from sympy.physics.units import speed_of_light, meter, second
>>> speed_of_light
speed_of_light
>>> speed_of_light.convert_to(meter/second)
299792458*meter/second

>>> from sympy.physics.units import liter
>>> liter.convert_to(meter**3)
meter**3/1000

property free_symbols

从数量中返回免费符号。

property is_prefixed

Whether or not the quantity is prefixed. Eg. \(kilogram\) is prefixed, but \(gram\) is not.

property scale_factor

与标准单位相比的量的总大小。

set_global_relative_scale_factor(scale_factor, reference_quantity)

设置在所有单位系统中有效的比例因子。

数量换算

几种简化包含单位对象的表达式的方法。

sympy.physics.units.util.convert_to(expr, target_units, unit_system='SI')

转换 expr 所有的单位和数量都表示为 target_units ，只要尺寸兼容。

target_units 可以是单个单位/数量，也可以是单位/数量的集合。

实例

>>> from sympy.physics.units import speed_of_light, meter, gram, second, day
>>> from sympy.physics.units import mile, newton, kilogram, atomic_mass_constant
>>> from sympy.physics.units import kilometer, centimeter
>>> from sympy.physics.units import gravitational_constant, hbar
>>> from sympy.physics.units import convert_to
>>> convert_to(mile, kilometer)
25146*kilometer/15625
>>> convert_to(mile, kilometer).n()
1.609344*kilometer
>>> convert_to(speed_of_light, meter/second)
299792458*meter/second
>>> convert_to(day, second)
86400*second
>>> 3*newton
3*newton
>>> convert_to(3*newton, kilogram*meter/second**2)
3*kilogram*meter/second**2
>>> convert_to(atomic_mass_constant, gram)
1.660539060e-24*gram

转换成动车组：

>>> convert_to(speed_of_light, [meter, second])
299792458*meter/second
>>> convert_to(3*newton, [centimeter, gram, second])
300000*centimeter*gram/second**2

转换为普朗克单位：

>>> convert_to(atomic_mass_constant, [gravitational_constant, speed_of_light, hbar]).n()
7.62963087839509e-20*hbar**0.5*speed_of_light**0.5/gravitational_constant**0.5