AniketTec/github-issues huggingface dataset:
Title: Refactor `Dataset.map` to reuse cache files mapped with different `num_proc`
State: closed

Fixes #7433

This refactor unifies `num_proc is None or num_proc == 1` and `num_proc > 1`; instead of handling them completely separately where one uses a list of kwargs and shards and the other just uses a single set of kwargs and `self`, by wrapping the `num_proc == 1` case in a list and making the difference just whether or not you use a pool, you set up either case to be able to load each other's cache files just by changing `num_shards`; `num_proc == 1` can sequentially load the shards of a dataset mapped `num_shards > 1` and map any missing shards

Other than the structural refactor, the main contribution of this PR is `existing_cache_file_map`, which uses a regex of `cache_file_name` and `suffix_template` to find existing cache files, grouped by their `num_shards`; using this data structure, we can reset `num_shards` to an existing set of cache files, and load them accordingly

Comments:
@lhoestq please let me know what you think about this.

It looks like I can't change the merge target to #7435, so it will look like there is a bunch of extra stuff until #7435 is in main.

@lhoestq Thanks so much for reviewing #7435! Now that that's merged, I think this PR is ready!! Can you kick off CI when you get the chance?

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/datasets/pr_7434). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

Do you mind kicking off CI again?

The change I made to support windows paths in 637c1600fe7dd601eff571fda446937bd96c5c84 ended up breaking causing these tests in [tests/test_data_files.py](https://github.com/huggingface/datasets/actions/runs/13858546629/job/38781008643#step:10:6991). When I removed `glob_pattern_to_regex` in 583c28e7560b9d6db2e13048731f41ec8fa11361, none of the tests failed. So I'm thinking the `unicode_escape` may be handling the what `glob_pattern_to_regex` was doing.


@lhoestq will you have a chance to review this today?

Any update?

> LGTM and sorry for the delay !
> 
> note that the CI failures are unrelated to this PR :)

Great job!

great job to @ringohoffman ! ;)
Title: `Dataset.map` ignores existing caches and remaps when ran with different `num_proc`
State: closed

### Describe the bug

If you `map` a dataset and save it to a specific `cache_file_name` with a specific `num_proc`, and then call map again with that same existing `cache_file_name` but a different `num_proc`, the dataset will be re-mapped.

### Steps to reproduce the bug

1. Download a dataset
```python
import datasets

dataset = datasets.load_dataset("ylecun/mnist")
```

```
Generating train split: 100%|██████████| 60000/60000 [00:00<00:00, 116429.85 examples/s]
Generating test split: 100%|██████████| 10000/10000 [00:00<00:00, 103310.27 examples/s]
```

2. `map` and cache it with a specific `num_proc`

```python
cache_file_name="./cache/train.map"
dataset["train"].map(lambda x: x, cache_file_name=cache_file_name, num_proc=2)
```

```
Map (num_proc=2): 100%|██████████| 60000/60000 [00:01<00:00, 53764.03 examples/s]
```

3. `map` it with a different `num_proc` and the same `cache_file_name` as before

```python
dataset["train"].map(lambda x: x, cache_file_name=cache_file_name, num_proc=3)
```

```
Map (num_proc=3): 100%|██████████| 60000/60000 [00:00<00:00, 65377.12 examples/s]
```

### Expected behavior

If I specify an existing `cache_file_name`, I don't expect using a different `num_proc` than the one that was used to generate it to cause the dataset to have be be re-mapped.

### Environment info

```console
$ datasets-cli env

- `datasets` version: 3.3.2
- Platform: Linux-5.15.0-131-generic-x86_64-with-glibc2.35
- Python version: 3.10.16
- `huggingface_hub` version: 0.29.1
- PyArrow version: 19.0.1
- Pandas version: 2.2.3
- `fsspec` version: 2024.12.0
```

Comments:
This feels related: https://github.com/huggingface/datasets/issues/3044

@lhoestq This comment specifically, I agree:

* https://github.com/huggingface/datasets/issues/3044#issuecomment-1239877570

> Almost a year later and I'm in a similar boat. Using custom fingerprints and when using multiprocessing the cached datasets are saved with a template at the end of the filename (something like "000001_of_000008" for every process of num_proc). So if in the next time you run the script you set num_proc to a different number, the cache cannot be used.
> 
> Is there any way to get around this? I am processing a huge dataset so I do the processing on one machine and then transfer the processed data to another in its cache dir but currently that's not possible due to num_proc mismatch.
Title: Error in code "Time to slice and dice" from course "NLP Course"
State: closed

### Describe the bug

When we execute code 
```
frequencies = (
    train_df["condition"]
    .value_counts()
    .to_frame()
    .reset_index()
    .rename(columns={"index": "condition", "condition": "frequency"})
)
frequencies.head()
```
answer should be like this

condition      | frequency
birth control | 27655
depression    | 8023
acne              | 5209
anxiety          | 4991
pain               | 4744

but he is different

frequency      | count
birth control  | 27655
depression    | 8023
acne              | 5209
anxiety          | 4991
pain               | 4744

this is not correct, correct code
```
frequencies = (
    train_df["condition"]
    .value_counts()
    .to_frame()
    .reset_index()
    .rename(columns={"index": "condition", "count": "frequency"})
)
````

### Steps to reproduce the bug

```
frequencies = (
train_df["condition"]
.value_counts()
.to_frame()
.reset_index()
.rename(columns={"index": "condition", "condition": "frequency"})
)
frequencies.head()
```

### Expected behavior


condition      | frequency
birth control | 27655
depression    | 8023
acne              | 5209
anxiety          | 4991
pain               | 4744

### Environment info

Google Colab

Comments:
You should open an issue in the NLP course website / github page. I'm closing this issue if you don't mind

ok, i don't mind, i'll mark the error there
Title: Improved type annotation
State: open

I've refined several type annotations throughout the codebase to align with current best practices and enhance overall clarity. Given the complexity of the code, there may still be areas that need further attention. I welcome any feedback or suggestions to make these improvements even better.

 - Fixes #7202 

Comments:
@lhoestq  Could someone please take a quick look or let me know if there’s anything I should change? Thanks!

could you fix the conflicts ? I think some type annotations have been improved since your first commit

It should be good now.
I'm happy to add more annotations or refine further if needed—just let me know!
Title: Row indexing a dataset with numpy integers
State: closed
Labels: description: New feature or request
name: enhancement

### Feature request

Allow indexing datasets with a scalar numpy integer type.

### Motivation

Indexing a dataset with a scalar numpy.int* object raises a TypeError. This is due to the test in `datasets/formatting/formatting.py:key_to_query_type`

``` python
def key_to_query_type(key: Union[int, slice, range, str, Iterable]) -> str:
    if isinstance(key, int):
        return "row"
    elif isinstance(key, str):
        return "column"
    elif isinstance(key, (slice, range, Iterable)):
        return "batch"
    _raise_bad_key_type(key)
```

In the row case, it checks if key is an int, which returns false when key is integer like but not a builtin python integer type. This is counterintuitive because a numpy array of np.int64s can be used for the batch case.

For example:

``` python
import numpy as np

import datasets

dataset = datasets.Dataset.from_dict({"a": [1, 2, 3, 4], "b": [5, 6, 7, 8]})

# Regular indexing
dataset[0]
dataset[:2]

# Indexing with numpy data types (expect same results)
idx = np.asarray([0, 1])
dataset[idx]  # Succeeds when using an array of np.int64 values
dataset[idx[0]]  # Fails with TypeError when using scalar np.int64
```

For the user, this can be solved by wrapping `idx[0]` in `int` but the test could also be changed in `key_to_query_type` to accept a less strict definition of int.

``` diff
+import numbers
+
def key_to_query_type(key: Union[int, slice, range, str, Iterable]) -> str:
+   if isinstance(key, numbers.Integral):
-   if isinstance(key, int):
        return "row"
    elif isinstance(key, str):
        return "column"
    elif isinstance(key, (slice, range, Iterable)):
        return "batch"
    _raise_bad_key_type(key)
```

Looking at how others do it, pandas has an `is_integer` definition that it checks which uses `is_integer_object` defined in `pandas/_libs/utils.pxd`:

``` cython
cdef inline bint is_integer_object(object obj) noexcept:
    """
    Cython equivalent of

    `isinstance(val, (int, np.integer)) and not isinstance(val, (bool, np.timedelta64))`

    Parameters
    ----------
    val : object

    Returns
    -------
    is_integer : bool

    Notes
    -----
    This counts np.timedelta64 objects as integers.
    """
    return (not PyBool_Check(obj) and isinstance(obj, (int, cnp.integer))
            and not is_timedelta64_object(obj))
```

This would be less flexible as it explicitly checks for numpy integer, but worth noting that they had the need to ensure the key is not a bool.

### Your contribution

I can submit a pull request with the above changes after checking that indexing succeeds with the numpy integer type. Or if there is a different integer check that would be preferred I could add that.

If there is a reason not to want this behavior that is fine too.


Comments:
Would be cool to be consistent when it comes to indexing with numpy objects, if we do accept numpy arrays we should indeed accept numpy integers. Your idea sounds reasonable, I'd also be in favor of adding a simple test as well
Title: Import order crashes script execution
State: open

### Describe the bug

Hello,

I'm trying to convert an HF dataset into a TFRecord so I'm importing `tensorflow` and `datasets` to do so.
Depending in what order I'm importing those librairies, my code hangs forever and is unkillable (CTRL+C doesn't work, I need to kill my shell entirely).

Thank you for your help
🙏 

### Steps to reproduce the bug

If you run the following script, this will hang forever : 
```python
import tensorflow as tf
import datasets

dataset = datasets.load_dataset("imagenet-1k", split="validation", streaming=True)
print(next(iter(dataset)))
```

however running the following will work fine (I just changed the order of the imports) :
```python
import datasets
import tensorflow as tf

dataset = datasets.load_dataset("imagenet-1k", split="validation", streaming=True)
print(next(iter(dataset)))
```

### Expected behavior

I'm expecting the script to reach the end and my case print the content of the first item in the dataset 
```
{'image': <PIL.JpegImagePlugin.JpegImageFile image mode=RGB size=408x500 at 0x70C646A03110>, 'label': 91}
```

### Environment info

```
$ datasets-cli env
- `datasets` version: 3.3.2
- Platform: Linux-6.8.0-1017-aws-x86_64-with-glibc2.35
- Python version: 3.11.7
- `huggingface_hub` version: 0.29.1
- PyArrow version: 19.0.1
- Pandas version: 2.2.3
- `fsspec` version: 2024.12.0
```

I'm also using `tensorflow==2.18.0`.

Comments:
Title: pyarrow.lib.arrowinvalid: cannot mix list and non-list, non-null values with map function
State: open

### Describe the bug

Encounter pyarrow.lib.arrowinvalid error with map function in some example when loading the dataset

### Steps to reproduce the bug

```
from datasets import load_dataset
from PIL import Image, PngImagePlugin

dataset = load_dataset("leonardPKU/GEOQA_R1V_Train_8K")
system_prompt="You are a helpful AI Assistant"
def make_conversation(example):
    prompt = []

    prompt.append({"role": "system", "content": system_prompt})
    prompt.append(
            {
                "role": "user", 
                "content": [
                        {"type": "image"},
                        {"type": "text", "text": example["problem"]},
                        ]
            }
        )
    return {"prompt": prompt}

def check_data_types(example):
    for key, value in example.items():
        if key == 'image':
            if not isinstance(value, PngImagePlugin.PngImageFile):
                print(value)
        if key == "problem" or key == "solution":
            if not isinstance(value, str):
                print(value)

    return example

dataset = dataset.map(check_data_types)
dataset = dataset.map(make_conversation)
```

### Expected behavior

Successfully process the dataset with map

### Environment info

datasets==3.3.1

Comments:
@lhoestq 

Can you try passing text: None for the image object ? Pyarrow expects all the objects to have the exact same type, in particular the dicttionaries in "content" should all have the keys "type" and "text"

The following modification on system prompt works, but it is different from the usual way to use it.
```
def make_conversation(example):
    prompt = []

    prompt.append({"role": "system", "content": [{"type": "text", "text": system_prompt}]})
    prompt.append(
            {
                "role": "user", 
                "content": [
                        {"type": "image"},
                        {"type": "text", "text": example["problem"]},
                        ]
            }
        )
    return {"prompt": prompt}
```

Good to know ! But yes Arrow / Parquet have this typing limitation (which is great to ensure data integrity, but constraining at the same time). It's is really blocking you, feel free to ping the arrow team / community if they plan to have a Union type or a JSON type

I encounter exactly the similar problem when using pyarrow. This issue truly helps a lot.

It would be very helpful if the error message could provide more context (such as the row index or the offending data) when this issue occurs. When loading large datasets, it's currently like finding a needle in a haystack because we don't know which specific entry caused the type mismatch.
Title: Shard Dataset at specific indices
State: open

I have a dataset of sequences, where each example in the sequence is a separate row in the dataset (similar to LeRobotDataset). When running `Dataset.save_to_disk` how can I provide indices where it's possible to shard the dataset such that no episode spans more than 1 shard. Consequently, when I run `Dataset.load_from_disk`, how can I load just a subset of the shards to save memory and time on different ranks?

I guess an alternative to this would be, given a loaded `Dataset`, how can I run `Dataset.shard` such that sharding doesn't split any episode across shards?

Comments:
Hi ! if it's an option I'd suggest to have one sequence per row instead.

Otherwise you'd have to make your own save/load mechanism

Saving one sequence per row is very difficult and heavy and makes all the optimizations pointless. How would a custom save/load mechanism look like?

You can use `pyarrow` for example to save/load individual arrow or parquet files and control what they contain
Title: Documentation on multiple media files of the same type with WebDataset
State: open

The [current documentation](https://huggingface.co/docs/datasets/en/video_dataset) on a creating a video dataset includes only examples with one media file and one json. It would be useful to have examples where multiple files of the same type are included. For example, in a sign language dataset, you may have a base video and a video annotation of the extracted pose. According to the WebDataset documentation, this should be able to be done with period separated filenames. For example:

```e39871fd9fd74f55.base.mp4
e39871fd9fd74f55.pose.mp4
e39871fd9fd74f55.json
f18b91585c4d3f3e.base.mp4
f18b91585c4d3f3e.pose.mp4
f18b91585c4d3f3e.json
... 
```

If you can confirm that this method of including multiple media files works with huggingface datasets and include an example in the documentation, I'd appreciate it.

Comments:
Yes this is correct and it works with huggingface datasets as well ! Feel free to include an example here: https://github.com/huggingface/datasets/blob/main/docs/source/video_dataset.mdx
Title: Index Error Invalid Ket is out of bounds for size 0 for code-search-net/code_search_net dataset
State: open

### Describe the bug

I am trying to do model pruning on sentence-transformers/all-mini-L6-v2 for the code-search-net/code_search_net dataset using INCTrainer class 
However I am getting below error

```
raise IndexError(f"Invalid Key: {key is our of bounds for size {size}")
IndexError: Invalid key: 1840208 is out of bounds for size 0
```

### Steps to reproduce the bug

Model pruning on the above dataset using the below guide 

https://huggingface.co/docs/optimum/en/intel/neural_compressor/optimization#pruning
### Expected behavior

The modsl should be successfully pruned 

### Environment info

Torch version: 2.4.1
Python version: 3.8.10

Comments:
Title: Attempt to fix multiprocessing hang by closing and joining the pool before termination
State: closed

https://github.com/huggingface/datasets/issues/6393 has plagued me on and off for a very long time. I have had various workarounds (one time combining two filter calls into one filter call removed the issue, another time making rank 0 go first resolved a cache race condition, one time i think upgrading the version of something resolved it). I don't know hf datasets well enough to fully understand the root cause, but I _think_ this PR fixes it.

Evidence: I have an LLM Foundry training yaml/script (datasets version 3.2.0) that results in a hang ~1/10 times (for a baseline for this testing, it was 2/36 runs that hung). I also reran with the latest datasets version (3.3.1) and got 4/36 hung. Installing datasets from this PR, I was able to successful run the script 144 times without a hang occurring. Assuming the base probability is 1/10, this should be more than enough times to have confidence it works.

After adding some logging, I could see that the code hung during the __exit__ of the mp pool context manager, after all shards had been processed, and the tqdm context manager had exited.

My best explanation: When multiprocessing pool __exit__ is called, it calls pool.terminate, which forcefully exits all the processes (and calls code related to this that I haven't looked at closely). I'm guessing this forceful termination has a bad interaction with some multithreading/multiprocessing that hf datasets does. If we instead call pool.close and pool.join before the pool.terminate happens, perhaps whatever that bad interaction is is able to complete gracefully, and then terminate call proceeds without issue.

If this PR seems good to you, I'd be very appreciative if you were able to do a patch release including it. Thank you!

@lhoestq 

Comments:
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/datasets/pr_7411). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

Thanks for the fix! We have been affected by this a lot when we try to use LLM Foundry with larger multimodal ICL datasets. 

@lorabit110 are you able to test it out for your case as well? Would be great to get a second validation that it actually fixes the issue. Thanks!
Title: Adding Core Maintainer List to CONTRIBUTING.md
State: closed
Labels: description: New feature or request
name: enhancement

### Feature request

I propose adding a core maintainer list to the `CONTRIBUTING.md` file.

### Motivation

The Transformers and Liger-Kernel projects maintain lists of core maintainers for each module. 
However, the Datasets project doesn't have such a list. 

### Your contribution

I have nothing to add here.

Comments:
@lhoestq

there is no per-module maintainer and the list is me alone nowadays ^^'

@lhoestq 
Oh... I feel for you. 
What are your criteria for choosing a core maintainer? 
It seems like it's too much work for you to manage all this code by yourself.

Also, if you don't mind, can you check this PR for me?
#7368 I'd like this to be added as soon as possible because I need it.
Title: Lazy loading of environment variables
State: open

### Describe the bug

Loading a `.env` file after an `import datasets` call does not correctly use the environment variables. 

This is due the fact that environment variables are read at import time:
https://github.com/huggingface/datasets/blob/de062f0552a810c52077543c1169c38c1f0c53fc/src/datasets/config.py#L155C1-L155C80

### Steps to reproduce the bug

```bash
# make tmp dir
mkdir -p /tmp/debug-env
# make .env file
echo HF_HOME=/tmp/debug-env/data > /tmp/debug-env/.env
# first load dotenv, downloads to /tmp/debug-env/data
uv run --with datasets,python-dotenv python3 -c \
'import dotenv; dotenv.load_dotenv("/tmp/debug-env/.env"); import datasets; datasets.load_dataset("Anthropic/hh-rlhf")' 
# first import datasets, downloads to `~/.cache/huggingface`
uv run --with datasets,python-dotenv python3 -c \
'import datasets; import dotenv; dotenv.load_dotenv("/tmp/debug-env/.env"); datasets.load_dataset("Anthropic/hh-rlhf")' 

```

### Expected behavior

I expect that setting environment variables with something like this:

```python3
if __name__ == "__main__":
    load_dotenv()
    main()
```
works correctly. 

### Environment info

    "datasets>=3.3.0",


Comments:
Many python packages out there, including `huggingface_hub`, do load the environment variables on import.
You should `load_dotenv()` before importing the libraries.

For example you can move all you imports inside your `main()` function
Title: Performance regression in `dataset.filter`
State: closed

### Describe the bug

We're filtering dataset of ~1M (small-ish) records. At some point in the code we do `dataset.filter`, before (including 3.2.0) it was taking couple of seconds, and now it takes 4 hours.

We use 16 threads/workers, and stack trace at them look as follows:
```
Traceback (most recent call last):
  File "/python/lib/python3.12/site-packages/multiprocess/process.py", line 314, in _bootstrap
    self.run()
  File "/python/lib/python3.12/site-packages/multiprocess/process.py", line 108, in run
    self._target(*self._args, **self._kwargs)
  File "/python/lib/python3.12/site-packages/multiprocess/pool.py", line 125, in worker
    result = (True, func(*args, **kwds))
                    ^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/datasets/utils/py_utils.py", line 678, in _write_generator_to_queue
    for i, result in enumerate(func(**kwargs)):
  File "/python/lib/python3.12/site-packages/datasets/arrow_dataset.py", line 3511, in _map_single
    for i, batch in iter_outputs(shard_iterable):
  File "/python/lib/python3.12/site-packages/datasets/arrow_dataset.py", line 3461, in iter_outputs
    yield i, apply_function(example, i, offset=offset)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/datasets/arrow_dataset.py", line 3390, in apply_function
    processed_inputs = function(*fn_args, *additional_args, **fn_kwargs)
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/datasets/arrow_dataset.py", line 6416, in get_indices_from_mask_function
    indices_array = indices_mapping.column(0).take(indices_array)
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "pyarrow/table.pxi", line 1079, in pyarrow.lib.ChunkedArray.take
  File "/python/lib/python3.12/site-packages/pyarrow/compute.py", line 458, in take
    def take(data, indices, *, boundscheck=True, memory_pool=None):
```

### Steps to reproduce the bug

1. Save dataset of 1M records in arrow
2. Filter it with 16 threads
3. Watch it take too long

### Expected behavior

Filtering done fast

### Environment info

datasets 3.3.0, python 3.12

Comments:
Thanks for reporting, I'll fix the regression today

I just released `datasets` 3.3.1 with a fix, let me know if it's good now :)

@lhoestq it fixed the issue.

This was (very) fast, thank you very much!