Components

To create a component dataclass, simply inherit from ComponentBase and define the fields as dataclass fields.

For example, to create a cantilever class that stores the cantilever frequency “f_c” and cantilever spring constant “k_c”, we can inherit the ComponentBase class and define the attributes as follows:

from mrfmsim.component import ComponentBase
from dataclasses import dataclass

@dataclass
class Cantilever(ComponentBase):
    f_c: float
    k_c: float


>>> cantilever = Cantilever(f_c=3000, k_c=1.0)
>>> cantilever.f_c
3000
>>> cantilever.k_c
1.0

>>> cantilever # dataclass output
Cantilever(f_c=3000, k_c=100.0)
>>> print(cantilever) # formatted output
Cantilever
    f_c = 3000
    k_c = 100.000

If we want additional attributes through calculation, instead of defining __init__ method, we can define a __post_init__ method. To specify that these are not instantiation variables, we specify that they are init=False in the dataclass field. See post-init processing.

from dataclasses import field
import numpy as np

@dataclass
class Cantilever(ComponentBase):
    k_c: float
    f_c: float = 5000
    omega: float = field(init=False)

    def __post_init__(self):
        self.omega = 2 * np.pi * self.f_c

>>> cantilever = Cantilever(k_c=100.0)
>>> cantilever.omega
31415.926535897932

>>> print(cantilever)
Cantilever
    f_c = 5000
    k_c = 100.000
    omega = 31415.927

In the above code, the cantilever frequency defaults to 5000 Hz.

To add units and formatted string output for the attributes, we can add “unit” and “format” to the dataclass field’ metadata.

@dataclass
class Cantilever(ComponentBase):
    k_c: float = field(metadata={"unit": "aN/nm", "format": ".3e"})
    f_c: float = field(metadata={"unit": "Hz", "format": ".3e"}, default=3000)
    omega: float = field(init=False, metadata={"unit": "rad/s", "format": ".3f"})

    def __post_init__(self):
        self.omega = 2 * np.pi * self.f_c

>>> cantilever = Cantilever(k_c=100.0)
>>> print(cantilever)
Cantilever
    k_c = 1.000e+02 aN/nm
    f_c = 3000 Hz
    omega = 18849.556 rad/s