Used to indicate an object of that type or that can instantiate that type. For example, "He 2+" is particle-like because it can be used to instantiate Particle.


An abbreviation for positional arguments.

charge number

The charge of a particle in units of elementary charge.

integration test

An integration test verifies that multiple software components work together as intended.

Compared to a unit test, an integration test is typically harder to write, slower to run, more difficult to maintain, and less useful at pinpointing the specific cause of a problem. However, integration tests are able to find problems that unit tests cannot. In particular, integration tests are able to find problems at the interfaces between different modules. On average, each integration test covers more lines of code than each related unit test. Because unit tests and integration tests complement each other, both are important constituents of a test suite.


An argument or parameter is keyword-only when the argument must be provided with the name of the corresponding parameter.

If z is a keyword-only parameter to f(z), then the argument 2 can be provided as f(z=2) but not f(2).


An abbreviation for keyword arguments.


An object is particle-like if it is a Particle or CustomParticle, or can be cast into one.

An element may be represented by a string containing the atomic symbol (case-sensitive), the name of the element, or an integer representing the atomic number. The element iron can be represented as "Fe", "iron", or 26.

An isotope may be represented by a string that contains an atomic symbol or element name, followed by a hyphen and the mass number (with no spaces in between). The isotope 56Fe can be represented as "Fe-56", or "iron-56". 2H can be represented by "D" or "deuterium", and 3H can be represented by "T" or "tritium".

An ion or neutral atom may be represented by a string that contains a representation of an element or isotope, followed by charge information which is typically an integer representing the charge number and a plus or minus sign to indicate the charge. For example, a deuteron may be represented as "D 1+" and 56Fe1+ may be represented as "Fe-56 1+".

A special particle may be represented by a string that contains the name of the particle (case insensitive) or a standard symbol for it (case insensitive). A neutron can be represented as "n" or "neutron"; a proton can be represented as "p+", "p", or "proton"; and an electron can be represented by "e-", "e", or "electron".

DimensionlessParticle instances are not particle-like because, without normalization information, they do not uniquely identify a physical particle.

For more complete details, refer to ParticleLike.

real number

Any numeric type that represents a real number. This could include a float, int, a dimensionless Quantity, or any of the numpy.number types. Note that if a PlasmaPy function expects a dimensional Quantity and a real number is provided, then the real number is often assumed to have the appropriate SI units.

unit test

A unit test verifies a single unit of behavior, does it quickly, and does it in isolation from other tests [Khorikov, 2020].

Unit tests are intended to provide fast feedback that help pinpoint the locations of errors. Unit tests often abide by the following pattern [Osherove, 2013]:

  1. Arrange: gather inputs and get the system to the state in which the test is expected to run.

  2. Act: make the system under test undertake the operation that is being tested.

  3. Assert: verify that the actual outcome of the act phase matches the expected outcome.

In a unit test for a function, the arrange phase involves collecting or constructing the inputs for the function. The act phase occurs when the function is called with those inputs. The assert phase is when the value returned by the function is compared to the expected result.