Python module for creating GDSII stream files, usually CAD layouts.





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Gdspy is a Python module for creation and manipulation of GDSII stream files. Key features for the creation of complex CAD layouts are included:

  • Boolean operations on polygons (AND, OR, NOT, XOR) based on clipping algorithm
  • Polygon offset (inward and outward rescaling of polygons)
  • Efficient point-in-polygon solutions for large array sets

Gdspy also includes a simple layout viewer.

Typical applications of Gdspy are in the fields of electronic chip design, planar lightwave circuit design, and mechanical engineering.

Future of Gdspy

In trying to improve the performance of Gdspy for large layouts, we ended up concluding that the best way to reach our goal was to rewrite the critical parts of the library as a C extension. It turns out that beside obvious functions, method calling has a big impact in performance due to the overhead it introduces. The best solution was to re-design the whole project as a C++ library with a thin Python wrapper: thus was born Gdstk, the GDSII Tool Kit.

Therefore, version 1.6 will be the last major release of Gdspy, with development focused only on bug fixes. Users are encouraged to move from Gdspy to Gdstk: although their API is not 100% compatible, the new module should be familiar enough to allow a quick transition.



  • Python (tested with versions 2.7, 3.6, 3.7, and 3.8)
  • Numpy
  • C compiler (needed only if built from source)
  • Tkinter (optional: needed for the LayoutViewer GUI)
  • Sphinx (optional: to build the documentation)

Linux / OS X

Option 1: using pip:

python -m pip install --user gdspy

Option 2: download the source from github and build/install with:

python install


The preferred option is to install pre-compiled binaries from here.

Installation via pip and building from source as above are also possible, but an appropriate build environment is required for compilation of the C extension modules.


The complete documentation is available here.

The source files can be found in the docs directory.


Help support Gdspy development by donating via PayPal

History of changes

Version 1.6.8 (Aug 2, 2021)

  • Fix in boolean for complex geometries that freeze the operation.

Version 1.6.7 (Jul 14, 2021)

  • Fixes in boolean for bugs with self-intersecting holes and holes horizontal edges.
  • Fix bug in warning message.

Version 1.6.6 (Jun 09, 2021)

  • Fix error in Path.smooth not finding _hobby function.
  • Allow precision specification in SVG output.

Version 1.6.5 (Jun 08, 2021)

  • Support GDSII files with 0-padding at the end.
  • Allow fixing and modifying GDSII file timestamps.
  • Thanks Troy Tamas and Joaquin Matres for the fixes

Version 1.6.4 (Apr 23, 2021)

  • Fix missing module import (thanks Troy Tamas for the fix).

Version 1.6.3 (Dec 28, 2020)

  • Fix bounding box edge case (thanks Troy Tamas for the fix).

Version 1.6.2 (Dec 18, 2020)

  • More efficient bounding box calculation (thanks to Troy Tamas for the contribution).
  • Fix Label creation bug.

Version 1.6.1 (Oct 22, 2020)

  • Fix SVG output when Label contains special characters.

Version 1.6 (Aug 12, 2020)

  • Added support for element properties.
  • Added transformation support to Cell.copy.
  • Layer/datatype filtering in get_polygons for Cell, CellReference and CellArray.
  • Layer/datatype filtering in LayoutViewer.
  • Removed global cache _bounding_boxes. Only cells cache their bounding boxes.
  • Bug fixes (thanks Daniel Hwang for the contributions).
  • Bug fix in Cell.copy where the whole dependency tree would be copied on a deep copy creation.

Version 1.5.2 (Feb 01, 2020)

  • Added support for importing GDSII files containing BOX elements.
  • Bug fix in GdsLibrary.extract (thanks collineps for finding the problem).

Version 1.5 (Dec 20, 2019)

  • New Cell.write_svg function to export an SVG image of the cell.
  • New GdsLibrary.new_cell function to quickly create and add cells to a library.
  • GdsLibrary.add can update references when a cell is overwritten.
  • Added GdsLibrary.remove to allow cells to be properly removed from libraries.
  • Added GdsLibrary.rename_cell to rename cells in libraries.
  • Added GdsLibrary.replace_references to easily replace referenced cells in libraries.
  • GdsLibrary.add can add dependencies recursively.
  • Iterating over GdsLibrary objects yields all its cells.
  • Iterating over Cell objects yield all its polygons, paths, labels and references.
  • Breaking change to *.to_gds functions in order to improve write efficiency (this should not be a problem for most users, since gdspy.write_gds and Cell.write_gds remain the same).
  • Breaking change: renamed GdsLibrary.cell_dict to GdsLibrary.cells.
  • Deprecated: gdspy.current_library, gdspy.write_gds, gdspy.fast_boolen, GdsLibrary.extract.
  • Bug fixes and better tests for FlexPath and RobustPath.

Version 1.4.3 (Nov 11, 2019)

  • Bug fix for FlexPath and RobustPath references.

Version 1.4.2 (Oct 01, 2019)

  • Bug fix in FlexPath.

Version 1.4.1 (Sep 20, 2019)

  • Bug fixes (thanks to DerekK88 and Sequencer for the patches).

Version 1.4 (May 18, 2019)

  • Revised documentation.
  • New FlexPath and RobustPath classes: more efficient path generation when using the original GDSII path specification.
  • New Curve class: SVG-like polygon creation.
  • Added PolygonSet.mirror (thanks to Daan Waardenburg for the contribution).
  • Added Path.bezier to create paths based on Bézier curves.
  • Added Path.smooth to create paths based on smooth interpolating curves.
  • Added get_gds_units to get units used in a GDSII file without loading.
  • Added get_binary_cells to load only the binary GDSII representation of cell from a file.
  • Added argument tolerance to Round, Path.arc, Path.turn, and Path.parametric to automatically control the number of points in the final polygons.
  • Added argument binary_cells to GDSII writing functions to support get_binary_cells.
  • Added argument rename_template to GdsLibrary.read_gds for flexible cell renaming (thanks to @yoshi74ls181 for the contribution).
  • Changed return value of slice to avoid creating empty PolygonSet.
  • Added argument timestamp to GDSII writing functions.
  • Improved Round to support creating ellipses.
  • Added support for unlimited number of points per polygon.
  • Added support for BGNEXTN and ENDEXTN when reading a GDSII file.
  • Polygon creation warnings are now controlled by poly_warnings.
  • Incorrect anchor in Label now raises an error, instead of emitting a warning.
  • Added correct support for radius in PolygonSet.fillet on a per-vertex basis.
  • Speed improvements in GDSII file generation (thanks to @fbeutel for the contribution) and geometry creation.
  • Font rendering example using matplotlib (thanks Hernan Pastoriza for the contribution).
  • Expanded test suite.

Version 1.3.2 (Mar 14, 2019)

  • Small fix for building on Mac OS X Mojave.

Version 1.3.1 (Jun 29, 2018)

  • PolygonSet becomes the base class for all polygons, in particular Polygon and Rectangle.
  • Added Cell.remove_polygons and Cell.remove_labels functions to allow filtering a cell contents based, for example, on each element's layer.
  • Added PolygonSet.scale utility method.
  • Added PolygonSet.get_bounding_box utility method.
  • Added argument timestamp to Cell.to_gds, GdsLibrary.write_gds and GdsWriter.
  • Added unit and precision arguments to GdsLibrary initialization and removed from its write_gds method.
  • Changed the meaning of argument unit in GdsLibrary.read_gds.
  • Improved slice to avoid errors when slicing in multiple positions at once.
  • Improved PolygonSet.fracture to reduce number of function calls.
  • Removed incorrect absolute flags for magnification and rotation in CellReference and CellArray.
  • Minor bug fixes.
  • Documentation fixes.
  • Removed deprecated classes and functions.

Version 1.2.1 (Dec 5, 2017)

  • GdsLibrary can be created directly from a GDSII file
  • Added return value to GdsLibrary.read_gds
  • Fixed return value of GdsLibrary.add

Version 1.2 (Oct 21, 2017)

  • Added new gdsii_hash function.
  • Added precision parameter to _chop, Polygon.fracture, Polygon.fillet, PolygonSet.fracture, PolygonSet.fillet, and slice.
  • Included labels in flatten operations (added get_labels to Cell, CellReference, and CellArray).
  • Fixed bug in the bounding box cache of reference copies.
  • Fixed bug in _chop that affected Polygon.fracture, PolygonSet.fracture, and slice.
  • Other minor bug fixes.

Version 1.1.2 (Mar 19, 2017)

  • Update clipper library to 6.4.2 to fix bugs introduced in the last update.
  • License change to Boost Software License v1.0.

Version 1.1.1 (Jan 27, 2017)

  • Patch to fix installation issue (missing README file in zip).

Version 1.1 (Jan 20, 2017)

  • Introduction of GdsLibrary to allow user to work with multiple library simultaneously.
  • Deprecated GdsImport in favor of GdsLibrary.
  • Renamed gds_print to write_gds and GdsPrint to GdsWriter.
  • Development changed to Python 3 (Python 2 supported via python-future).
  • Added photonics example.
  • Added test suite.
  • Clipper library updated to last version.
  • Fixed inside function sometimes reversing the order of the output.
  • Fixed rounding error in fast_boolean.
  • Fixed argument deep_copy being inverted in Cell.copy.
  • Bug fixes introduced by numpy (thanks to Adam McCaughan for the contribution).

Version 1.0 (Sep 11, 2016)

  • Changed to "new style" classes (thanks to Adam McCaughan for the contribution).
  • Added a per-point radius specification for Polygon.fillet (thanks to Adam McCaughan for the contribution).
  • Added inside fucntion to perform point-in-polygon tests (thanks to @okianus for the contribution).
  • Moved from distutils to setuptools for better Windows support.

Version 0.9 (Jul 17, 2016)

  • Added option to join polygons before applying an offset.
  • Added a translate method to geometric entities (thanks John Bell for the commit).
  • Bug fixes.

Version 0.8.1 (May 6, 2016)

  • New fast_boolean function based on the Clipper library with much better performance than the old boolean.
  • Changed offset signature to also use the Clipper library (this change breaks compatibility with previous versions).
  • Bug fix for error when importing some labels from GDSII files.

Version 0.7.1 (June 26, 2015)

  • Rebased to GitHub.
  • Changed source structure and documentation.

Version 0.7 (June 12, 2015)

  • New feature: offset function.
  • New GdsPrint class for incremental GDSII creation (thanks to Jack Sankey for the contribution).

Version 0.6 (March 31, 2014)

  • Default number of points for Round, Path.arc, and Path.turn changed to resolution of 0.01 drawing units.
  • Path.parametric accepts callable final_distance and final_width for non-linear tapering.
  • Added argument ends to PolyPath.
  • Added (limited) support for PATHTYPE in GdsImport.
  • A warning is issued when a Path curve has width larger than twice its radius (self-intersecting polygon).
  • Added a random offset to the patterns in LayoutViewer.
  • LayoutViewer shows cell labels for referenced cells.
  • get_polygons returns (referenced) cell name if depth < 1 and by_spec is True.
  • Bug fix in get_bounding_box when empty cells are referenced.
  • Bug fixes in GdsImport and many speed improvements in bounding box calculations (thanks to Gene Hilton for the patch).

Version 0.5 (October 30, 2013) - NOT COMPATIBLE WITH PREVIOUS VERSIONS

  • Major LayoutViewer improvements (not backwards compatible).
  • The layer argument has been repositioned in the argument list in all functions (not backwards compatible).
  • Renamed argument by_layer to by_spec (not backwards compatible).
  • Error is raised for polygons with more vertices than possible in the GDSII format.
  • Removed the global state variable for default datatype.
  • Added get_datatypes to Cell.
  • Added argument single_datatype to Cell.flatten.
  • Removed gds_image and dropped the optional PIL dependency.

Version 0.4.1 (June 5, 2013)

  • Added argument axis_offset to Path.segment allowing creation of asymmetric tapers.
  • Added missing argument x_reflection to Label.
  • Created a global state variable to override the default datatype.
  • Bug fix in CellArray.get_bounding_box (thanks to George McLean for the fix)

Version 0.4 (October 25, 2012)

  • Cell.get_bounding_box returns None for empty cells.
  • Added a cache for bounding boxes for faster computation, especially for references.
  • Added support for text elements with Label class.
  • Improved the emission of warnings.
  • Added a tolerance parameter to boolean.
  • Added better print descriptions to classes.
  • Bug fixes in boolean involving results with multiple holes.

Version 0.3.1 (May 24, 2012)

  • Bug fix in the fracture method for PolygonSet.

Version 0.3a (May 03, 2012)

  • Bug fix in the fracture method for Polygon and PolygonSet.

Version 0.3 (April 25, 2012)

  • Support for Python 3.2 and 2.7
  • Further improvements to the boolean function via caching.
  • Added methods get_bounding_box and get_layers to Cell.
  • Added method top_level to GdsImport.
  • Added support for importing GDSII path elements.
  • Added an argument to control the verbosity of the import function.
  • Layer -1 (referenced cells) sent to the bottom of the layer list by default in LayoutViewer
  • The text and background of the layer list in LayoutViewer now reflect the colors of the outlines and canvas backgroung.
  • Changed default background color in LayoutViewer
  • Thanks to Gene Hilton for the contributions!

Version 0.2.9 (December 14, 2011)

  • Attribute Cell.cell_list changed to Cell.cell_dict.
  • Changed the signature of the operation in boolean.
  • Order of cells passed to LayoutViewer is now respected in the GUI.
  • Complete re-implementation of the boolean function as a C extension for improved performance.
  • Removed precision argument in boolean. It is fixed at 1e-13 for merging close points, otherwise machine precision is used.
  • gds_image now accepts cell names as input.
  • Added optional argument depth to get_polygons
  • Added option to convert layers and datatypes in imported GDSII cells.
  • Argument exclude_layers from LayoutViewer changed to hidden_layers and behavior changed accordingly.
  • Shift + Right-clicking on a layer the layer-list of LayoutVIewer hides/unhides all other layers.
  • New buttons to zoom in and out in LayoutViewer.
  • Referenced cells below a configurable depth are now represented by theirs bounding boxes in LayoutViewer.

Version 0.2.8 (June 21, 2011)

  • GDSII file import
  • GDSII output automatically include required referenced cells.
  • gds_print also accepts file name as input.
  • Outlines are visible by default in LayoutViewer.
  • Added background color option in LayoutViewer.
  • Right-clicking on the layer list hides/unhides the target layer in LayoutViewer.
  • Cell.cell_list is now a dictionary indexed by name, instead of a list.
  • Added option to exclude created cells from the global list of cells kept in Cell.cell_list.
  • CellReference and CellArray accept name of cells as input.
  • Submodules lost their own __version__.

Version 0.2.7 (April 2, 2011)

  • Bug fixed in the boolean, which affected the way polygons with more vertices then the maximum were fractured.
  • gds_image accepts an extra color argument for the image background.
  • Screenshots takes from LayoutViewer have the same background color as the viewer.
  • The functions boolean and slice now also accept CellReference and CellArray as input.
  • Added the method fracture to Polygon and PolygonSet to automatically slice polygons into parts with a predefined maximal number of vertices.
  • Added the method fillet to Polygon and PolygonSet to round corners of polygons.

Version 0.2.6 (February 28, 2011)

  • When saving a GDSII file, ValueError is raised if cell names are duplicated.
  • Save screenshot from LayoutViewer.
  • gds_image accepts cells, instead of lists.
  • Outlines supported by gds_image.
  • LayoutViewer stores bounding box information for all visited layers to save rendering time.

Version 0.2.5 (December 10, 2010)

  • Empty cells no longer break the LayoutViewer.
  • Removed the gds_view function, superseded by the LayoutViewer, along with all dependencies to matplotlib.
  • Fixed a bug in boolean which affected polygons with series of collinear vertices.
  • Added a function to slice polygons along straight lines parallel to an axis.

Version 0.2.4 (September 04, 2010)

  • Added shortcut to Extents in LayoutViewer: Home or a keys.
  • PolygonSet is the new base class for Round, which might bring some incompatibility issues with older scripts.
  • Round elements, PolyPath, L1Path, and Path arc, turn and parametric sections are now automatically fractured into pieces defined by a maximal number of points.
  • Default value for max_points in boolean changed to 199.
  • Removed the flag to disable the warning about polygons with more than 199 vertices. The warning is shown only for Polygon and PolygonSet.
  • Fixed a bug impeding parallel parametric paths to change their distance to each other.

Version 0.2.3 (August 09, 2010)

  • Added the PolyPath class to easily create paths with sharp corners.
  • Allow None as item in the colors parameter of LayoutViewer to make layers invisible.
  • Added color outline mode to LayoutViewer (change outline color with the shift key pressed)
  • Increased the scroll region of the LayoutViewer canvas
  • Added a fast scroll mode: control + drag 2nd mouse button
  • Created a new sample script

Version 0.2.2 (July 29, 2010)

  • Changed the cursor inside LayoutViewer to standard arrow.
  • Fixed bugs with the windows version of LayoutViewer (mouse wheel and ruler tool).

Version 0.2.1 (July 29, 2010)

  • Bug fix: gds_image displays an error message instead of crashing when PIL is not found.
  • Added class LayoutViewer, which uses Tkinter (included in all Python distributions) to display the GDSII layout with better controls then the gds_view function. This eliminates the matplotlib requirement for the viewer functionality.
  • New layer colors extending layers 0 to 63.

Version 0.2.0 (July 19, 2010)

  • Fixed a bug on the turn method of Path.
  • Fixed a bug on the boolean function that would give an error when not using Polygon or PolygonSet as input objects.
  • Added the method get_polygons to Cell, CellReference and CellArray.
  • Added a copy method to Cell.
  • Added a flatten method to Cell to remove references (or array references) to other cells.
  • Fracture boolean output polygons based on the number of vertices to respect the 199 GDSII limit.

Version 0.1.9 (June 04, 2010)

  • Added L1Path class for Manhattan geometry (L1 norm) paths.

Version 0.1.8 (May 10, 2010)

  • Removed the argument fill from gds_view and added a more flexible one: style.
  • Fixed a rounding error on the boolean operator affecting polygons with holes.
  • Added a rotate method to PolygonSet.
  • Added a warning when PolygonSet has more than 199 points
  • Added a flag to disable the warning about polygons with more than 199 points.
  • Added a turn method to Path, which is easier to use than arc.
  • Added a direction attribute to Path to keep the information used by the segment and turn methods.

Version 0.1.7 (April 12, 2010)

  • New visualization option: save the geometry directly to an image file (lower memory use).
  • New functionality added: boolean operations on polygons (polygon clipping).
  • All classes were adapted to work with the boolean operations.
  • The attribute size in the initializer of class Text does not have a default value any longer.
  • The name of the argument format in the function gds_view was changed to fill (to avoid confusion with the built-in function format).

Version 0.1.6 (December 15, 2009)

  • Sample script now include comments and creates an easier to understand GDSII example.
  • Improved floating point to integer rounding, which fixes the unit errors at the last digit of the precision in the GDSII file.
  • Fixed the font for character 5.
  • Added a flag to gds_view to avoid the automatic call to
  • In gds_view, if a layer number is greater than the number of formats defined, the formats are cycled.

Version 0.1.5a (November 15, 2009)

  • Class Text correctly interprets \n and \t characters.
  • Better documentation format, using the Sphinx engine and the numpy format.

Version 0.1.4 (October 5, 2009)

  • Class Text re-written with a different font with no overlaps and correct size.

Version 0.1.3a (July 29 2009)

  • Fixed the function to_gds of class Rectangle.

Version 0.1.3 (July 27, 2009)

  • Added the datatype field to all elements of the GDSII structure.

Version 0.1.2 (July 11, 2009)

  • Added the gds_view function to display the GDSII structure using the matplotlib module.
  • Fixed a rotation bug in the CellArray class.
  • Module published under the GNU General Public License (GPL)

Version 0.1.1 (May 12, 2009)

  • Added attribute cell_list to class Cell to hold a list of all Cell created.
  • Set the default argument cells=Cell.cell_list in the function gds_print.
  • Added member to calculate the area for each element type.
  • Added member to calculate the total area of a Cell or the area by layer.
  • Included the possibility of creating objects in user-defined units, not only nanometers.

Version 0.1.0 (May 1, 2009)

  • Initial release.

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