Detailed API Documentation

Documention of the classes and methods provided by leveldiagram

Level Diagram Constructors

class leveldiagram.LD(graph, ax=None, default_label='left_text', level_defaults=None, coupling_defaults=None, wavy_defaults=None, deflection_defaults=None, use_ld_kw=False)[source]

Basic Level Diagram drawing class.

This class is used to draw a level diagram based on a provided Directional Graph. The nodes of this graph define the energy levels, the edges define the couplings.

Note

In keeping with the finest matplotlib traditions, default options and behavior will produce a reasonable output from a graph. To get more refined diagrams, global options can be set by passing keyword argument dictionaries to the constructor. Options per level or coupling can be set by setting keyword arguments in the dictionaries of the nodes and edges of the graph.

Examples

>>> nodes = (0,1,2)
>>> edges = ((0,1), (1,2))
>>> graph = nx.DiGraph()
>>> graph.add_nodes_from(nodes)
>>> graph.add_edges_from(edges)
>>> d = ld.LD(graph)
>>> d.draw()
Basic 3-level diagram with 2 couplings using all default settings
Parameters:

  • graph (networkx.DiGraph) –

    Graph object that defines the system to diagram

    Beyond the arguments provided to the Coupling artist primitive, each coupling plotted by LD can also take the following parameters (which are defined as edge attributes on the graph).

    • hidden: bool - Tells LD to ignore this coupling

    • start_anchor: str or 2-element tuple - Controls the start anchor point

    • stop_anchor: str or 2-element tuple - Controls the stop anchor point

    • detuning: float - How much to detune the coupling from the transition by. Defined in x-coordinate units.

    • wavy: bool - Make coupling arrow a sine wave. Uses default options if wavy specific options not provided.

    • deflect: bool - Make coupling a deflected, circular coupling. Uses default options if deflect specific options not provided.

  • ax (matplotlib.axes.Axes, optional) – Axes to add the diagram to. If None, creates a new figure and axes. Default is None.

  • default_label (str, optional) – Sets which text label direction to use for default labelling, which is the node index inside a key. Valid options are 'left_text', 'right_text', 'top_text', 'bottom_text'. If ‘none’, no default labels are not generated.

  • level_defaults (dict, optional) – EnergyLevel default values for whole diagram. Provided values override class defaults. If None, use class defaults.

  • coupling_defaults (dict, optional) – Coupling default values for whole diagram. Provided values override class defaults. If None, use class defaults.

  • wavy_defaults (dict, optional) – Wavy specific Coupling default values for whole diagram. Provided values override class defaults. If None, use class defaults.

  • deflection_defaults (dict, optional) – Deflection specific Coupling default values for whole diagram. Provided values override class defaults. If None, use class defaults.

  • use_ld_kw (bool) –

_coupling_defaults = {'arrowsize': 0.15, 'label_kw': {'fontsize': 'large'}}

Coupling default parameters dictionary

_deflection_defaults = {'deflection': 0.25}

Default parameters for a deflection

_level_defaults = {'color': 'k', 'text_kw': {'fontsize': 'large'}, 'width': 1}

EnergyLevel default parameters dictionary

_wavy_defaults = {'halfperiod': 0.1, 'waveamp': 0.05}

Default parameters for a wavy coupling

couplings: Dict[Tuple[int, int], Coupling]

Stores couplings to be drawn

draw()[source]

Add artists to the figure.

This calls matplotlib.axes.Axes.autoscale_view() to ensure plot ranges are increased to account for objects.

It may be necessary to increase plot margins to handle labels near edges of the plot.

generate_couplings()[source]

Creates the Coupling and WavyCoupling artisits from the graph edges.

They are saved to the couplings dictionary.

generate_levels()[source]

Creates the EnergyLevel artists from the graph nodes.

They are saved to the levels dictionary.

levels: Dict[int, EnergyLevel]

Stores levels to be drawn

Artist Primitives

Customized matplotlib artist primitives

class leveldiagram.artists.Coupling(start, stop, arrowsize, deflection=0.0, waveamp=0.0, halfperiod=0, arrowratio=1, tail=False, arrow_kw=None, label='', label_offset='center', label_rot=False, label_flip=False, label_kw=None, **kwargs)[source]

Bases: Line2D

Coupling artist for showing couplings between levels.

This artist is a conglomeration of artists.

Sufficient methods are overridden from the base Line2D class to ensure the other artists are rendered whenever the main artist is rendered.

Parameters:

  • start (2-element collection) – Coupling start location in data coordinates

  • stop (2-element collection) – Coupling end location in data coordinates

  • arrowsize (float) – Size of arrowheads in x-data coordinates

  • deflection (float, optional) – Amount to bend the center of the coupling arrow away from linear. Defined in y-coordintes. Default is 0 or no deflection.

  • waveamp (float, optional) – Amplitude of sine wave modulation of the coupling arrow. Defined in y-coordinates. Default is 0 or no waviness.

  • halfperiod (float, optional) – Length of half-period of sine modulation. Defined in x-coordinates. Both waveamp and period must be non-zero to get modulation. Default is 0 or no waviness.

  • arrowratio (float, optional) – Aspect ratio of the arrowhead. Default is 1 for equal aspect ratio.

  • tail (bool, optional) – Whether to draw an identical arrowhead at the coupling base. Default is False.

  • arrow_kw (dict, optional) – Dictionary of keyword arguments to pass to matplotlib.patches.Polygon constructor. Note that keyword arguments provided to this function will clobber identical keys provided here.

  • label (str, optional) – Label string to apply to the coupling. Default is no label.

  • label_offset (str, optional) – Offset direction for the label. Options are 'center', 'left', and 'right'. Default is center of the coupling line.

  • label_rot (bool, optional) – Label is justified along the coupling arrow axis if True. Default is False, so label is oriented along x-axis always.

  • label_flip (bool, optional) – Apply a 180 degree rotation to the label. Default is False.

  • label_kw (dict, optional) – Dictionary of keyword arguments to pass to the matplotlib.text.Text constructor.

  • kwargs – Optional keyword arguments passed to the matplotlib.lines.Line2D constructor and the matplotlib.patches.Polygon constructor for the arrowhead. Note that 'color' will be automatically changed to 'facecolor' for the arrowhead to avoid extra lines.

draw(renderer)[source]

Draw the Artist (and its children) using the given renderer.

This has no effect if the artist is not visible (.Artist.get_visible returns False).

Parameters:

renderer (~matplotlib.backend_bases.RendererBase subclass.) –

Notes

This method is overridden in the Artist subclasses.

init_arrowheads(**kwargs)[source]

Creates the arrowhead(s) for the coupling as matplotlib polygon objects.

Parameters:

kwargs – Optional keyword arguments to pass to the matplotlib.patches.Polygon constructor.

init_label(label, label_offset, label_rot, label_flip, **label_kw)[source]

Creates the coupling label text object.

Parameters:

  • label (str) – Label string to apply to the coupling.

  • label_offset (str) – Offset direction for the label. Options are 'center', 'left', and 'right'.

  • label_rot (bool) – Label will be justified along the coupling arrow axis if True.

  • label_flip (bool) – Apply a 180 degree rotation to the label.

  • label_kw – Keyword arguments to pass to the matplotlib.text.Text constructor.

init_path()[source]

Calculates the desired path for the line of the coupling.

The returned path is a line relative to the x-axis of the correct length. Transforms are used to move and rotate this path to the end location. This method of making the couplings is a little convoluted, but it allows for simple definition of very general paths (line sine waves) without distortions.

Returns:

  • x (numpy.ndarray) – x-coordinates of the data points for the un-rotated, un-translated path

  • y (numpy.ndarray) – y-coordinates of the data points for the un-rotated, un-translated path

Return type:

Tuple[ndarray, ndarray]

set_axes(axes)[source]
set_figure(figure)[source]

Set the .Figure instance the artist belongs to.

Parameters:

fig (~matplotlib.figure.Figure) –

set_transform(transform)[source]

Set the artist transform.

Parameters:

t (~matplotlib.transforms.Transform) –

class leveldiagram.artists.EnergyLevel(energy, xpos, width, right_text='', left_text='', top_text='', bottom_text='', text_kw=None, **kwargs)[source]

Bases: Line2D

Energy level artist.

This object also implements a number of potential Text artists for labelling. It also includes helper methods for getting the exact coordinates of anchor points for connected coupling arrows and the like.

Parameters:

  • energy (float) – y-axis position of the level

  • xpos (float) – x-axis position of the level

  • width (float) – Width of the level line, in units of the x-axis

  • right_text (str, optional) – Text to put to the right of the level

  • left_text (str, optional) – Text to put to the left of the level

  • top_text (str, optional) – Text to put above the level

  • bottom_text (str, optional) – Text to put below the level

  • text_kw (dict, optional) – Dictionary of keyword-arguments passed to matplotlib.text.Text

  • kwargs – Passed to the matplotlib.lines.Line2D constructor

draw(renderer)[source]

Draw the Artist (and its children) using the given renderer.

This has no effect if the artist is not visible (.Artist.get_visible returns False).

Parameters:

renderer (~matplotlib.backend_bases.RendererBase subclass.) –

Notes

This method is overridden in the Artist subclasses.

get_anchor(loc='center')[source]

Returns an anchor on the level in plot coordinates.

Parameters:

loc (str or collection of 2 elements) – What reference point to return. 'center', 'left', 'right' gives those points of the level. A 2-element iterable is interpreted as offsets from the center location.

Raises:

TypeError – If loc is not accepted string or a 2-element iterable.

Return type:

ndarray

get_center()[source]

Returns coordinates of the center of the level line.

Returns:

x,y coordinates

Return type:

numpy.ndarray

get_left()[source]

Returns coordinates of the left of the level line.

Returns:

x,y coordinates

Return type:

numpy.ndarray

get_right()[source]

Returns coordinates of the right of the level line.

Returns:

x,y coordinates

Return type:

numpy.ndarray

set_axes(axes)[source]
Parameters:

axes (Axes) –

set_data(x, y)[source]

Set the x and y data.

Parameters:

*args ((2, N) array or two 1D arrays) –

set_figure(figure)[source]

Set the .Figure instance the artist belongs to.

Parameters:

fig (~matplotlib.figure.Figure) –

set_transform(transform)[source]

Overridden to add padding offsets to labels.

text_labels: Dict[str, Text]

Text label objects to add to the level

Utilities

Miscellaneous utility functions

leveldiagram.utils.about()[source]

Display version of leveldiagram and critical dependencies.

leveldiagram.utils.bra_str(s)[source]

Put a bra around the string in matplotlib.

Parameters:

s (Any) – Object to be converted to a string and placed inside a bra.

Returns:

A string that will render as \(\left\langle\text{s}\right|\)

Return type:

str

leveldiagram.utils.deep_update(mapping, *updating_mappings)[source]

Helper function to update nested dictionaries.

Lifted from pydantic

Returns:

Deep-updated copy of mapping

Return type:

dict

Parameters:

  • mapping (dict) –

  • updating_mappings (dict) –

leveldiagram.utils.ket_str(s)[source]

Put a ket around the string in matplotlib.

Parameters:

s (Any) – Object to be converted to string and placed inside a ket.

Returns:

A string that will render as \(\left|\text{s}\right\rangle\)

Return type:

str