String not interfaced to IStream

[JJMinton]

Updating from 7.5.1 to 7.8.1, I am trying to replace BRepTools_ShapeSet.ReadFromString with BRepTools_ShapeSet.Read as I believe is the result of #1301 .

The resulting error was:

>>> from OCC.Core.BRepTools import BRepTools_ShapeSet
>>> BRepTools_ShapeSet().Read("foo")
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/miniconda3/envs/occwl_dev/lib/python3.9/site-packages/OCC/Core/TopTools.py", line 2880, in Read
    return _TopTools.TopTools_ShapeSet_Read(self, *args)
TypeError: Wrong number or type of arguments for overloaded function 'TopTools_ShapeSet_Read'.
  Possible C/C++ prototypes are:
    TopTools_ShapeSet::Read(std::istream &,Message_ProgressRange const &)
    TopTools_ShapeSet::Read(TopoDS_Shape &,std::istream &)

I am installing from conda in a docker container:

# syntax=docker/dockerfile:1.4
FROM --platform=linux/amd64 python:3.9 as base

RUN python -m pip install --upgrade pip

FROM base as dev

# Insgtall OCC requirements
RUN apt-get update
RUN  apt-get install -y ffmpeg libsm6 libxext6

# Install conda
RUN mkdir -p ~/miniconda3 && \
    wget https://repo.anaconda.com/miniconda/Miniconda3-latest-Linux-x86_64.sh -O ~/miniconda3/miniconda.sh && \
    bash ~/miniconda3/miniconda.sh -b -u -p /miniconda3 && \
    rm -rf ~/miniconda3/miniconda.sh && \
    /miniconda3/bin/conda init bash

ARG PROJ_DIR=/proj
ARG PIP_CACHE=/root/.cache/pip
WORKDIR ${PROJ_DIR}

# Create conda environment
COPY environment.yml .
RUN --mount=type=cache,target=/miniconda3/pkgs,id=conda \
    /miniconda3/bin/conda env create -f environment.yml

where environment.yml is

name: occwl_dev
channels:
  - conda-forge
  - defaults
  - anaconda
dependencies:
  - python=3.9
  - numpy
  - pythonocc-core=7.8.1
  - networkx
  - wxPython
  - pydeprecate

The full context is this PR

[tpaviot]

Confirmed. Under investiagtion. If your need is to load a TopoDS_Shape from a serialization, you can try:

from OCC.Core.BRepTools import breptools
the_shape = breptools.ReadFromString("foo")

this is how shape pickling is implemented for the TopoDS_Shape class.

[Andrej730]

@tpaviot

1. Can you please help narrow down, from which OCC or PythonOCC version this change occurred? Can confirm that it occurred after 7.7.2 but was it 7.8.0 or 7.8.1?

2. Is new way

from OCC.Core.BRepTools import breptools
brep_string = ""
shape = breptools.ReadFromString(brep_string)

is equivalent to the old snippet below or there are some caveats?

This snippet seems to be used often by users - https://github.com/search?q=BRepTools_ShapeSet+ReadFromString+NbShapes+language%3APython&type=code

from OCC.Core.BRepTools import BRepTools_ShapeSet
brep_string = ""
shape_set = BRepTools_ShapeSet()
shape_set.ReadFromString(brep_string)
shape = shape_set.Shape(shape_set.NbShapes())

[JJMinton]

Thanks for the response @tpaviot, any progress with this? Is there any help I could provide? Unfortunately, we're looking for all the subshapes so can't make do with breptools.

[tpaviot]

@JJMinton I can fix the regression by just resetting the ReadFromString method as it used to be before the latest release, it will be published in the next release (the 7.8.2 release of occt might come in a few days/weeks).

Note that the ReadFromString method did use breptools:

static TopoDS_Shape ReadFromString(const std::string & src) {
   std::stringstream s(src);
   TopoDS_Shape shape;
   BRep_Builder b;
   BRepTools::Read(shape, s, b);
   return shape;
}

@Andrej730