# Python containers conversion to Fish **URL:** \ **Category:** Wish List\ **Tags:** python\ **Created:** [March 29, 2024, 5:16pm UTC](https://forum.itascainternational.com/t/python-containers-conversion-to-fish/1388 "2024-03-29T17:16:10Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Theophile](https://yyz1.discourse-cdn.com/flex031/user_avatar/forum.itascainternational.com/theophile/32/299_2.png) [@Theophile](https://forum.itascainternational.com/u/Theophile)\ **Post date:** [March 29, 2024, 5:16pm UTC](https://forum.itascainternational.com/t/python-containers-conversion-to-fish/1388/1 "2024-03-29T17:16:10Z")
Hi everyone! We are extensively using the Python API in our 3DEC computations, so first of all, thanks for that! As of today (and at least in 3DEC), conversion of Python containers to Fish objects are not supported, except for length 2 `list`/`tuple`/`numpy.arrays` (+ `vec.vec2`) that would convert to `vector2` and length 3 of the same objects (+ `vec.vec3`) that would convert to `vector3`. Interestingly, conversion is more flexible on the other way around: | Fish | Python | | --- | --- | | list (of any length) | tuple | | map | dict | | vector2 | vec.vec2 | | vector3 | vec.vec3 | | array | _not supported_ | | matrix | _not supported_ | | tensor | _not supported_ | I have no idea of how much work it would require, but would it be possible to complete the conversion of containers between Python and Fish in a near future update? Maybe not all conversions, but being able to convert `tuples` and `numpy.arrays` from Python to Fish, and Fish arrays to `numpy.arrays` in Python would be great. Thanks a lot! Regards Théophile ---
**Author:** ![Huy](https://avatars.discourse-cdn.com/v4/letter/h/c5a1d2/32.png) [@Huy](https://forum.itascainternational.com/u/Huy)\ **Post date:** [April 2, 2024, 8:51am UTC](https://forum.itascainternational.com/t/python-containers-conversion-to-fish/1388/2 "2024-04-02T08:51:02Z")
Hello Théophile, We added the conversions for more containers in the recent version (list python → list fish, dict python → map fish). We can add matrix \<=\> numpy array tensor \<=\> vec.tens3 For array, I think it’s more like multi-dimensional lists. ---
**Author:** ![Theophile](https://yyz1.discourse-cdn.com/flex031/user_avatar/forum.itascainternational.com/theophile/32/299_2.png) [@Theophile](https://forum.itascainternational.com/u/Theophile)\ **Post date:** [April 2, 2024, 1:01pm UTC](https://forum.itascainternational.com/t/python-containers-conversion-to-fish/1388/3 "2024-04-02T13:01:40Z")
Hi @Huy ! Ok, thanks. As of 3DEC versions 7.00.161 and 9.00.167, setting a Fish list from a Python’s one still raises a `ValueError: unknown type in conversion from PyObject to QVariant tuple`. In the meantime, I wrote Python functions that I give at the end of this post in case it could be of any help to some users. They deal with the following Python to Fish conversions: - `list`/`tuple` to `list` - `dict` to `map` - `numpy.ndarray` to `array` Notice it is only a temporary solution until your native implementation since it is underoptimized (e.g., 1 s for instantiating à 100,000 elements array from Python to Fish versus 0.5 ms in pure Python). Besides, since it uses a bypass through strings, the float format precision might falsify the values in Fish. Cheers! Regards Théophile PS: the code ```python """ Temporary solution to pass containers to Fish Warning ------- Just a workaround until container conversion is natively dealt with through Itasca's Python API. This workaround is underoptimized, e.g., a random (100, 1000)-shaped array takes 0.5ms to run in Python console, and conversion to Fish takes ~1s (depends of course on the machine it's running on, but it's the 2000x ratio that matters). """ import itasca as it import numpy as np def format_fish_list(iterator, transformers={}): """ Formatting a Python iterator to a Fish list Parameters ---------- iterator: iterator (preferably list or tuple) The sequence to convert to Fish list Note ---- Nested iterators are supported transformers: dict Custom type-to-string formatters with (key, val) = (type to format, formatting function), see examples Returns ------- out: str The formatted iterator as a Fish list constructor Examples -------- >>> test = (1, 'foo', 'bar', ('nested', True), 3.2548e-10) >>> format_fish_list(test) 'list.seq(1, "foo", "bar", list.seq("nested", true), 3.2548e-10)' Custom converters >>> test = (99, {'a': 1, 'b': 2}) >>> format_fish_list(test) KeyError: >>> def my_dict_conv(d): ... return format_fish_list(d.values()) >>> format_fish_list(test, {dict: my_dict_conv}) >>> test = (99, {'a': 1, 'b': 2}) 'list.seq(99, list.seq(1, 2))' """ transform = { bool: lambda x: str(x).lower(), int: lambda x: str(x), float: lambda x: str(x), list: format_fish_list, str: lambda x: f'"{x}"', tuple: format_fish_list, } transform.update(transformers) items = ', '.join([ transform[type(item)](item) for item in iterator ]) return f'list.seq({items})' def format_fish_array(arr): """ Formatting a numpy array to a Fish array Parameters ---------- arr: np.ndarray The array to format Returns ------- out: str The formatted array as a Fish array constructor Examples -------- >>> import numpy as np >>> test = np.array(((1,2,3), (4,5,6))) >>> format_fish_array(test) 'array(list.seq(1, 4, 2, 5, 3, 6), 2, 3)' """ items = arr.flatten('F').tolist() shape = ', '.join([str(n) for n in arr.shape]) return f'array({format_fish_list(items)}, {shape})' def format_fish_map(dictionary): """ Formatting a dictionary a Fish map Parameters ---------- dictionary: dict The dictionary to format Returns ------- out: str The formatted dict as a Fish map constructor Examples -------- >>> test = {'hello': 'world', -62: 1.e10, True: False} >>> format_fish_map(test) 'map(list.seq("hello", -62, true), list.seq("world", 10000000000.0, false))' """ keys, values = zip(*dictionary.items()) return f'map({format_fish_list(keys)}, {format_fish_list(values)})' def format_fish_container( container, var_name=None, instantiate=False, transformers={} ): """ Formatting a Python container to a Fish constructor Parameters ---------- container: list/tuple/dict/np.ndarray The container to set in Fish var_name: str The name of the Fish variable for storing the container. If None, the formatted container has no associated variable. instantiate: bool Whether the container should be instantiated on the fly in Fish (var_name must not be None). transformers: dict Custom type-to-string formatters with (key, val) = (type to format, formatting function), see doc from format_fish_list() Examples -------- List/tuple >>> test = (1, -15., 'foo', ('nested', True), 3.2548e-10) >>> format_fish_container(test) 'list.seq(1, -15.0, "foo", list.seq("nested", true), 3.2548e-10)' >>> format_fish_container(demo_seq, 'test') 'test=list.seq(1, -15.0, "foo", list.seq("nested", true), 3.2548e-10)' Setting variable on-the-fly >>> format_fish_container(demo_seq, 'test', instantiate=True) 'test=list.seq(1, -15.0, "foo", list.seq("nested", true), 3.2548e-10)' >>> it.fish.get('test') (1, -15.0, 'foo', ('nested', True), 3.2548e-10) Array >>> test_arr = np.array(((1.,2.,3.),(4.,5.,6.))) >>> format_fish_container(test_arr, 'test_arr', instantiate=True) 'test_arr=array(list.seq(1.0, 4.0, 2.0, 5.0, 3.0, 6.0), 2, 3)' Dict >>> test_dict = {'hey': 'yo', -62: 1.e3, True: False} >>> format_fish_container(test_dict, 'test_dict', instantiate=True) 'test_dict=map(list.seq("hey", -62, true), list.seq("yo", 1000.0, false))' """ if isinstance(container, np.ndarray): items = format_fish_array(container) elif isinstance(container, dict): items = format_fish_map(container) else: items = format_fish_list(container, transformers) if var_name is not None: items = f'{var_name}={items}' if instantiate: it.command(f'[{items}]') else: assert not instantiate, 'Cannot instantiate with no var_name' return items if __name__ == ' __main__': # List/tuple test = (1, -15., 'foo', ('nested', True), 3.2548e-10) print(format_fish_container(test)) print(format_fish_container(test, 'test')) assert not it.fish.has('test') format_fish_container(test, 'test', instantiate=True) assert it.fish.has('test') assert test==it.fish.get('test') # Array: test with a silly formatting test_arr = np.array((((1,),(2,),(3,)),((4,),(5,),(6,)))) format_fish_container(test_arr, 'test_arr', instantiate=True) assert it.fish.has('test_arr') # Dict test_dict = {'hey': 'yo', -62: 1.e3, True: False} format_fish_container(test_dict, 'test_dict', instantiate=True) assert test_dict==it.fish.get('test_dict') ``` ---
**Author:** ![Huy](https://avatars.discourse-cdn.com/v4/letter/h/c5a1d2/32.png) [@Huy](https://forum.itascainternational.com/u/Huy)\ **Post date:** [April 2, 2024, 1:49pm UTC](https://forum.itascainternational.com/t/python-containers-conversion-to-fish/1388/4 "2024-04-02T13:49:39Z")
You can check maybe the next subversion. Note that the fish array is not homogeneous as ndarray. So I think ndarray should be equivalent to fish matrix ---
**Author:** ![Theophile](https://yyz1.discourse-cdn.com/flex031/user_avatar/forum.itascainternational.com/theophile/32/299_2.png) [@Theophile](https://forum.itascainternational.com/u/Theophile)\ **Post date:** [April 2, 2024, 2:38pm UTC](https://forum.itascainternational.com/t/python-containers-conversion-to-fish/1388/5 "2024-04-02T14:38:20Z")
Oh, ok, thanks for the hint. In previous versions of 3DEC, I think arrays stored homogeneous types. Converting to a matrix would restrict to 2-dimensional arrays, but it’s true that it’s their most common use. Cheers! ---
**Author:** ![vl.diachenko](https://avatars.discourse-cdn.com/v4/letter/v/9dc877/32.png) [@vl.diachenko](https://forum.itascainternational.com/u/vl.diachenko)\ **Post date:** [September 4, 2025, 3:10pm UTC](https://forum.itascainternational.com/t/python-containers-conversion-to-fish/1388/6 "2025-09-04T15:10:07Z")
Any updates? I’m trying to pass an array to a FISH function: ```auto fish define import_data(arr) loop foreach local value arr io.out("Processing " + string(value)) endloop end ``` ```python import itasca as it data = [1, 2, 3, 4, 5] it.fish.call_function("import_data", (data,)) ``` But I get this error: ```python AttributeError Traceback (most recent call last) AttributeError: Slot 'CommManager::_dispatch(PyObject)' not found. --------------------------------------------------------------------------- ValueError Traceback (most recent call last) Cell In[55], line 1 ----> 1 it.fish.call_function("import_data", (data,)) ValueError: Cannot iterate over objects of type Integer. ``` FLAC3D 9.4.32.