Cannot load CLoader with pyyaml

Question

I'm working on a python project using pyyaml. I need to run it in a Docker container based on bitnami/minideb:jessie. Python version is 2.7.9. The original code is using CLoader and I cannot change it currently. Any reason CLoader fails to load but Loader is fine ?

>>> import yaml
>>> yaml.__version__
'3.12'
>>> from yaml import Loader
>>> from yaml import CLoader
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: cannot import name CLoader
>>>

I cannot figure out what I'm missing here. Any idea ?

Running it from the Docker image python:2.7.9 does not raise any error then:

$ docker run -ti python:2.7.9 bash
#/ python
>>> from yaml import CLoader
>>> from yaml import Loader
>>>

Answer 1

By default, the setup.py script checks whether LibYAML is installed and if so, builds and installs LibYAML bindings.

This is the minimum to get CLoader compiled and installed.

FROM ubuntu:20.04
RUN apt-get update && apt-get install -y \
    python3 python3-dev python3-pip gcc libyaml-dev
RUN pip3 install pyyaml
# verify
RUN python3 -c "import yaml; yaml.CLoader"

Answer 2

I ran into the same problem. You need to install the libyaml-dev package, then install libyaml and pyyaml from source. Here's the complete Dockerfile for minideb:jessie:

FROM bitnami/minideb:jessie

RUN apt-get update
RUN apt-get install -y \
        automake \
        autoconf \
        build-essential \
        git-core \
        libtool \
        libyaml-dev \
        make \
        python \
        python-dev \
        python-pip

RUN pip install --upgrade pip
RUN pip install Cython==0.29.10

RUN mkdir /libyaml
WORKDIR /libyaml
RUN git clone https://github.com/yaml/libyaml.git . && \
    git checkout dist-0.2.2 && \
    autoreconf -f -i && \
    ./configure && \
    make && \
    make install

RUN mkdir /pyyaml
WORKDIR /pyyaml
RUN git clone https://github.com/yaml/pyyaml.git . && \
    git checkout 5.1.1 && \
    python setup.py install

RUN python -c "import yaml; from yaml import CLoader; print 'Loaded CLoader!'"