June gems

content/blog/2020-06-29-june-20-community-gems.md

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+---
+title: June '20 Community Gems
+date: 2020-06-29
+description: |
+  A roundup of technical Q&A's from the DVC community. This month, we discuss 
+  migrating to DVC 1.0, the new pipeline format, and our Python API.
+descriptionLong: |
+  A roundup of technical Q&A's from the DVC community. This month, we discuss 
+  migrating to DVC 1.0, the new pipeline format, and our Python API.
+picture: 2020-06-29/Gems_June_20.png
+author: elle_obrien
+commentsUrl: https://discuss.dvc.org/t/june-20-community-gems/426
+tags:
+  - Discord
+  - Gems
+  - MinIO
+  - Pipeline
+  - Python API
+  - Optimization
+---
+
+## Highlights from Discord
+
+Here are some Q&A's from our Discord channel that we think are worth sharing.
+
+### Q: I just upgraded to DVC 1.0. I've got some pipeline stages currently saved as `.dvc` files. [Is there an easy way to convert the old `.dvc` format to the new `dvc.yaml` standard?](https://discord.com/channels/485586884165107732/563406153334128681/725019219930120232)
+
+Yes! You can easily transfer the stages by hand: `dvc.yaml` is designed for
+manual edits in any text editor, so you can type your old stages in and then
+delete the old `.dvc` files. We also have a
+[migration script](https://gist.github.com/skshetry/07a3e26e6b06783e1ad7a4b6db6479da)
+available, although we can't provide long-term support for it.
+
+Learn more about the `dvc.yaml` format in our
+[brand new docs](https://dvc.org/doc/user-guide/dvc-files-and-directories#dvcyaml-file)!
+
+https://media.giphy.com/media/JYpTAnhT0EI2Q/giphy.gif
+
+_Just like this but with technical documentation._
+
+### Q: After I pushed my local data to remote storage, I noticed the file names are different in my storage repository- they're hash values. [Can I make them more meaningful names?](https://discord.com/channels/485586884165107732/563406153334128681/717737163122540585)
+
+No, but for a good reason! What you're seeing are cached files, and they're
+stored with a special naming convention that makes DVC versioning and addressing
+possible- these file names are how DVC deduplicates data (to avoid keeping
+multiple copies of the same file version) and ensures that each unique version
+of a file is immutable. If you manually overwrote those filenames you would risk
+breaking Git version control. You can
+[read more about how DVC uses this file format in our docs](https://dvc.org/doc/user-guide/dvc-files-and-directories#structure-of-cache-directory).
+
+It sounds like you're looking for ways to interact with DVC-tracked objects at a
+high level of abstraction, meaning that you want to interface with the original
+filenames and not the machine-generated hashes used by DVC. There are a few
+secure and recommended ways to do this:
+
+- If you want to see a human-readable list of files that are currently tracked
+  by DVC, try the `dvc list`
+  command-[read up on it here](https://dvc.org/doc/command-reference/list).
+- Check out our
+  [data registry tutorial](https://dvc.org/doc/use-cases/data-registries#data-registries)
+  to see how the commands `dvc get` and `dvc import` are used to download and
+  share DVC-tracked artifacts. The syntax is built for an experience like using
+  a package manager.
+- The [DVC Python API](https://dvc.org/doc/api-reference) gives you programmatic
+  access to DVC-tracked artifacts, using human-readable filenames.
+
+### Q: [Is it better practice to `dvc add` data files individually, or to add a directory containing multiple data files?](https://discord.com/channels/485586884165107732/563406153334128681/722141190312689675)
+
+If the directory you're adding is logically one unit (for example, it is the
+whole dataset in your project), we recommend using `dvc add` at the directory
+level. Otherwise, add files one-by-one. You can
+[read more about how DVC versions directories in our docs](https://dvc.org/doc/user-guide/dvc-files-and-directories#structure-of-cache-directory).
+
+### Q: [Do you have any examples of using DVC with MinIO?](https://discord.com/channels/485586884165107732/563406153334128681/722780202844815362)
+
+We don't have any tutorials for this use case exactly, but it's a very
+straightforward modification from
+[our basic use cases](https://dvc.org/doc/use-cases). The key difference when
+using MinIO or a similar S3-compatible storage (like DigitalOcean Spaces or IBM
+Cloud Object Storage) is that in addition to setting remote data storage, you
+must set the `endpointurl` too. For example:
+
+```dvc
+$ dvc remote add -d myremote s3://mybucket/path/to/dir
+$ dvc remote modify myremote endpointurl https://object-storage.example.com
+```
+
+Read up on configuring supported storage
+[in our docs](https://dvc.org/doc/command-reference/remote/add#supported-storage-types).
+
+### Q: [If I have a folder containing many data files, is there any advantage to zipping the folder and DVC tracking the `.zip`?](https://discord.com/channels/485586884165107732/563406153334128681/714922184455225445)
+
+There are a few things to consider:
+
+- **CPU time.** Even though it can be faster to pull a single file than a
+  directory (though not in all cases, since we can parallelize directory
+  downloads), the tradeoff is the time needed to unzip your data. Depending on
+  your constraints, this can be expensive and undesirable.
+
+- **Deduplication.** DVC deduplicates on the file level. So if you add one
+  single file to a directory, DVC will save only that file, not the whole
+  dataset again. If you use a zipped directory you won't get this benefit. In
+  the long run, this could be more expensive in terms of storage space for your
+  DVC cache and remote if the contents of your dataset change frequently.
+
+Generally, we would recommend first trying a plain unzipped directory. DVC is
+designed to work with large numbers of files (on the order of millions) and has
+the latest release (DVC 1.0) has
+[optimizations built for this purpose exactly](https://dvc.org/blog/dvc-1-0-release#data-transfer-optimizations).
+
+### [Q: Can I execute a `dvc push` with the DVC Python API inside a Python script?](https://discord.com/channels/485586884165107732/485596304961962003/718419219288686664)
+
+Currently, our [Python API](https://dvc.org/doc/api-reference#python-api)
+doesn't support commands like `dvc push`,`dvc pull`, or `dvc status`. It is
+designed for interfacing with objects tracked by DVC. That said, CLI commands
+are basically calling `dvc.repo.Repo` object methods. So if you want to use
+commands from within Python code, you could try creating a `Repo` object with
+`r = Repo({root_dir})` and then `r.push()`. Please note that we don't officially
+support this use case yet.
+
+Of course, you can also run DVC commands from a Python script using `sys` or a
+similar library for issuing system commands.
+
+### [Q: Does the `dvc pipeline` command for visualizing pipelines still work in DVC 1.0?](https://discord.com/channels/485586884165107732/485596304961962003/717682556203565127)
+
+Most of the `dvc pipeline` functionality- like `dvc pipeline show --ascii` to
+print out an ASCII diagram of your pipeline- has been migrated to a new command,
+`dvc dag`. This function is written for our new pipeline format. Check out
+[our new docs](https://dvc.org/doc/command-reference/dag#dag) for an example.
+
+### [Q: Is there a way to create a DVC pipeline stage without running the commands in that stage?](https://discord.com/channels/485586884165107732/485596304961962003/715271980978405447)
+
+Yes. Say you have a Python script, `train.py`, that takes in a dataset `data`
+and outputs a model `model.pkl`. To create a DVC pipeline stage corresponding to
+this process, you could do so like this:
+
+```dvc
+$ dvc run -n train
+        -d train.py -d data
+        -o model.pkl
+        python train.py
+```
+
+However, this would automatically rerun the command `python train.py`, which is
+not necessarily desirable if you have recently run it, the process is time
+consuming, and the dependencies and outputs haven't changed. You can use the
+`--no-exec` flag to get around this:
+
+```dvc
+$ dvc run --no-exec
+        -n train
+        -d train.py -d data
+        -o model.pkl
+        python train.py
+```
+
+This flag can also be useful when you want to define the pipeline on your local
+machine but plan to run it later on a different machine (perhaps an instance in
+the cloud).
+[Read more about the `--no-exec` flag in our docs.](https://dvc.org/doc/command-reference/run)
+
+One other approach worth mentioning is that you can manually edit your
+`dvc.yaml` file to add a stage. If you add a stage this way, pipeline commands
+won't be executed until you run `dvc repro`.