Expression

Expression(parameter, expression)

Numerical parametric expression object.

Args

• parameter (str | Sequence[str]): Independent variable name, or sequence of names.
• expression (str | tuple[str, str | float] | Sequence[str | tuple[str, str | float]]): Expression to be evaluated as a function of the parameter(s). A list of expressions can also be used.

When using multiple expressions, they are evaluated in sequence and previous results are available to subsequent expressions by their name. Expression names can be set by using tuples with (name, expression).

Examples

>>> e = pf.Expression("u", "2 * u")
>>> e(1.5)
3.0
>>> e = pf.Expression("u", [("a", 2), ("b", "u^(a - 1)"), "a * b"])
>>> e(3)
array([2., 3., 6.])
>>> e = pf.Expression(
...     ["x", "y"], ["sqrt(x^2 + y^2)", "atan2(y, x)"]
... )
>>> e(1, -1)
array([ 1.41..., -0.78...])

Note

Expression strings support the following:

• Constants: e, pi
• Operators: +, -, *, /, %, ^ (exponent)
• Functions: abs, acos, and, asin, atan2, atan, ceil, cos, cosh, exp, floor, if, ln, log (same as ln), log10, max, min, or, pow, sin, sinh, sqrt, tan, tanh

Functions max and min only accept 2 arguments.

Functions if, and, or are equivalent to the following python expressions:

• if(a, b, c) == b if a > 0 else c
• and(a, b) == b if a > 0 else a
• or(a, b) == a if a > 0 else b

Methods

Method	Description
copy	Create a copy of this expression.

copy

copy(self)

Create a copy of this expression.

Returns

New copy.

Attributes

Attribute	Description
expressions	list[tuple[str, str | float]]: Object expressions as a list (read only).
parameters	list[str]: Object parameters as a list (read only).
properties	Properties: Object properties.

expressions

list[tuple[str, str | float]]: Object expressions as a list (read only).

parameters

list[str]: Object parameters as a list (read only).

properties

Properties: Object properties.