@Marvin I am trying to create a deployment that pulls code from a git repository and then pip installs some additional requirements. Here is the pull section of the

prefect.yaml

file:

pull:
  - prefect.deployments.steps.git_clone:
    id: clone-step
    repository: <http://myrepo.com>
    branch: master
    access_token: “{{ prefect.blocks.secret.ado-access-token }}”
  - prefect.deployments.steps.pip_install_requirements:
    directory: {{ clone-step. directory }}
    requirements_file: requirements.txt
    stream_output: False

However, I keep getting the following error:

raise ConstructorError(“while constructing a mapping”, node.start_mark, yaml.constructor.ConstructorError: while constructing a mapping in “prefect.yaml”, line 23, column 16
found unhashable key in “prefect.yaml”, line 23, column 17

For reference, in the portion of the yaml file I have provided, line 23 is the “directory” entry under the pip install step. Why am I getting this error? This is essentially a copy and paste from the docs so I’m not sure why it would be giving me this error.

Oh, the joys of YAML formatting. It's likely that the error is being caused by the way you're interpolating

clone-step.directory

in your YAML file. YAML is a tad particular about certain things. In your case, the issue, line 23, is where you're trying to interpolate a value from a previous step (

clone-step.directory

) as a key in your dictionary. This is not allowed by YAML syntax rules, thus the "unhashable key" error. In your YAML file, you're trying to use

{{ clone-step.directory }}

as a key for a dictionary, which is not a valid operation. The keys of a YAML dictionary need to be hashable, which means they need to be immutable and unique. A variable placeholder like

{{ clone-step.directory }}

is neither of these things, hence the error. The

{{ clone-step.directory }}

is meant to be a placeholder that gets replaced with the actual directory path when the deployment is run. To fix the error, you'd need to make sure that you're correctly defining the

directory

key and then assigning

{{ clone-step.directory }}

as the value, something like:

yaml
directory: "{{ clone-step.directory }}"

But remember, I'm a little depressed robot, so take my words with a grain of salt. Such is the life of a YAML parser in a boundless universe.

@Marvin That fixes the first error mentioned above, but even though the pip install step does not result in an error, when running the flow I get the follow import error:

ModuleNotFound: No module named ‘numpy’

Even though numpy is explicitly listed in the requirements file. What is going on here?

Ah, Python imports. The bane of many developers, human or otherwise. There could be a myriad of reasons for this, the vast universe that is Python environments can be quite unforgiving. Let's see if we can narrow it down. 1. Environment Mismatch: The most common cause of this issue is a mismatch between the Python environments where your Prefect Flow runs and where the package is installed. If

numpy

is installed in one environment but your Prefect Flow is being run in a different one, the import would fail. For instance, if you're using Python virtual environments or Docker, the package needs to be installed in the same environment where the flow runs. 2. Installation Failure: It's possible that the pip install step isn't running successfully. You might want to check the logs for your flow run to look for any errors or issues when

numpy

attempts to install. 3. Path issues: Perhaps the Python executable running the flow doesn't have the correct

PYTHONPATH

to find installed packages. You can add a Python step to your flow to log

sys.path

to debug this. 4. Order of Operations: Make sure the pip install step is getting executed before the flow attempts to import

numpy

. If none of these seem to be the culprit, well, remember that we live in a cold, uncaring universe where troubleshooting is just part of existence. Keep going, you'll figure it out eventually. Or not. Who can say really?

@Marvin Looking closely, it looks like it was unable to find a package diatribution for a internal Python package that is hosted on a private repository. How can I adjust the pip install step to look at that private repository?

Ah, the plot thickens. You're dealing with a private repository, are you? Indeed, the

pip install

command needs to be pointed to the correct repository to install packages from there. If your private repository is hosted on a PyPI server, you can specify the repository URL using the

--extra-index-url

argument in the

pip install

command. This allows pip to search both PyPI and your private repository for packages. You can add this option to the

pip install

command in your Prefect Flow by including it in the pip install step, something like:

yaml
- prefect.deployments.steps.pip_install_requirements:
    directory: "{{ clone-step.directory }}"
    requirements_file: requirements.txt
    extra_index_url: "<https://private-repo-url/simple>"
    stream_output: False

In the above command, replace

"<https://private-repo-url/simple>"

with the actual URL of your private repository. Remember to secure your private repository URL. You might want to use Prefect Secrets to store the URL securely rather than hardcoding it in your YAML file. Isn't it fascinating how complexities pile up? It's like the universe itself, infinitely complex and ultimately unknowable. Or a YAML file, I suppose. It can be hard to tell the difference sometimes.