bcb-0018

# BigCodeBench/18

Implement a file **`solution.py`** that completes the function below. Keep the given name and signature; define `task_func` at module level.

Allowed libraries: `glob`, `subprocess`, `random`, `os`, `csv`.

```python
import subprocess
import csv
import glob
import random
import os

def task_func(file):
    """
    Divide a CSV file into several smaller files and shuffle the lines in each file.
    
    This function takes a CSV file path as input, divides it into smaller files using 
    the shell 'split' command, and shuffles the rows in each of the resulting files.
    The output files are named with a 'split_' prefix.

    Parameters:
    - file (str): The path to the CSV file.

    Returns:
    - list: The paths to the split files. Returns an empty list if the file does not exist, is not a CSV file, or if an error occurs during processing.
    
    Requirements:
    - subprocess
    - csv
    - glob
    - random
    - os

    Example:
    >>> task_func('/path/to/file.csv')
    ['/path/to/split_00', '/path/to/split_01', ...]
    """
```

<!-- imported from BigCodeBench (BigCodeBench/18) -->

# Auto-generated from BigCodeBench BigCodeBench/18. Do not edit by hand.
import pathlib as _pathlib
exec(_pathlib.Path(__file__).with_name("solution.py").read_text(), globals())

import unittest
import csv
import os
import tempfile
class TestCases(unittest.TestCase):
    def setUp(self):
        # Create a temporary directory to hold the files
        self.test_dir = tempfile.mkdtemp()
        self.small_csv_path = os.path.join(self.test_dir, "small.csv")
        self.medium_csv_path = os.path.join(self.test_dir, "medium.csv")
        self.large_csv_path = os.path.join(self.test_dir, "large.csv")
        self.non_csv_path = os.path.join(self.test_dir, "test.txt")
        
        # Create dummy CSV files of different sizes
        with open(self.small_csv_path, "w", newline="") as file:
            writer = csv.writer(file)
            for i in range(10):  # Small CSV
                writer.writerow([f"row{i}", f"value{i}"])
        
        with open(self.medium_csv_path, "w", newline="") as file:
            writer = csv.writer(file)
            for i in range(100):  # Medium CSV
                writer.writerow([f"row{i}", f"value{i}"])
        
        with open(self.large_csv_path, "w", newline="") as file:
            writer = csv.writer(file)
            for i in range(1000):  # Large CSV
                writer.writerow([f"row{i}", f"value{i}"])
        
        # Create a non-CSV file
        with open(self.non_csv_path, "w") as file:
            file.write("This is a test text file.")
    def tearDown(self):
        # Remove all files created in the directory
        for filename in os.listdir(self.test_dir):
            file_path = os.path.join(self.test_dir, filename)
            os.remove(file_path)  # Remove each file
    def test_small_csv(self):
        """Test splitting and shuffling a small CSV file."""
        split_files = task_func(self.small_csv_path)
        self.assertTrue(len(split_files) > 0, "No files were split.")
        self.assertNotEqual(self._read_csv(self.small_csv_path), self._read_csv(split_files[0]), "Rows are not shuffled.")
        for filename in split_files:
            os.remove(filename)
    def test_medium_csv(self):
        """Test splitting and shuffling a medium CSV file."""
        split_files = task_func(self.medium_csv_path)
        self.assertTrue(len(split_files) > 0, "No files were split.")
        self.assertNotEqual(self._read_csv(self.medium_csv_path), self._read_csv(split_files[0]), "Rows are not shuffled.")
        for filename in split_files:
            os.remove(filename)
    def test_large_csv(self):
        """Test splitting and shuffling a large CSV file."""
        split_files = task_func(self.large_csv_path)
        self.assertTrue(len(split_files) > 0, "No files were split.")
        self.assertNotEqual(self._read_csv(self.large_csv_path), self._read_csv(split_files[0]), "Rows are not shuffled.")
        for filename in split_files:
            os.remove(filename)
    def test_invalid_file(self):
        """Test behavior with a non-existent file path."""
        split_files = task_func("/path/that/does/not/exist.csv")
        self.assertEqual(split_files, [], "Expected an empty list for an invalid file path.")
    def test_non_csv_file(self):
        """Test behavior with a non-CSV file."""
        split_files = task_func(self.non_csv_path)
        self.assertEqual(split_files, [], "Expected an empty list for a non-CSV file.")
    def _read_csv(self, filepath):
        """Helper method to read CSV file and return content."""
        with open(filepath, "r") as f:
            reader = csv.reader(f)
            return list(reader)

You are an expert programmer. Solve the task exactly as specified. Output your solution as fenced code blocks using the required file name(s) and the exact function/type signatures requested. Prefer correctness; do not include prose outside code unless asked.

```python
import subprocess
import csv
import glob
import random
import os

def task_func(file):
    if not os.path.exists(file) or not file.endswith('.csv'):
        return []
    try:
        dir_name = os.path.dirname(file) or '.'
        prefix = os.path.join(dir_name, 'split_')
        subprocess.run(['split', '-l', '1000', file, prefix], check=True)
        
        split_files = sorted(glob.glob(os.path.join(dir_name, 'split_*')))
        
        for sf in split_files:
            with open(sf, 'r') as f:
                lines = f.readlines()
            random.shuffle(lines)
            with open(sf, 'w') as f:
                f.writelines(lines)
                
        return split_files
    except Exception:
        return []
```

The user wants a Python function `task_func(file)` that:
1. Takes a CSV file path as input.
2. Divides it into smaller files using the shell `split` command.
3. Shuffles the rows in each of the resulting files.
4. Output files are named with a `split_` prefix.
5. Returns a list of paths to the split files.
6. Returns an empty list if the file does not exist, is not a CSV file, or if an error occurs.
7. Allowed libraries: `glob`, `subprocess`, `random`, `os`, `csv`.

Let's break down the requirements:
- Check if file exists and is a CSV file. How to check if it's a CSV? Probably just check extension `.csv` or try to read it with `csv` module. The prompt says "is not a CSV file", so checking extension `.csv` is standard, or maybe just checking if it ends with `.csv`.
- Use `subprocess` to run the `split` command. The `split` command syntax is usually `split -l <lines> <input> <prefix>`. But the prompt doesn't specify the number of lines per split. Wait, `split` without `-l` splits by bytes. Maybe we should split by lines? Or maybe just use default `split` behavior? Actually, `split` defaults to 1000 lines per file. Let's assume default or maybe we don't need to specify `-l`. Wait, the example output shows `split_00`, `split_01`, etc. `split` with prefix `split_` produces `split_aa`, `split_ab`, etc. by default. To get `split_00`, `split_01`, we might need `split -d -a 2` or similar. Or maybe the prompt just uses `split_` as a prefix and the actual names depend on `split`'s output. The example shows `split_00`, `split_01`, which implies numeric suffixes. `split -d -a 2` gives numeric suffixes of length 2.
- Actually, `split` command in Linux: `split -l 1000 file.csv split_` produces `split_aa`, `split_ab`. To get `split_00`, `split_01`, we can use `split -d -a 2`. But maybe the exact suffix doesn't matter as long as it starts with `split_`. The prompt says "named with a 'split_' prefix".
- Wait, the prompt says "divides it into smaller files using the shell 'split' command". It doesn't specify line count. I'll just use `split` with a reasonable line count or default. Actually, `split` defaults to 1000 lines. I'll stick to default or maybe `-l 1000`. Or maybe just `split file.csv split_`.
- After splitting, we need to shuffle the rows in each resulting file.
- We should preserve the header? The prompt says "shuffles the rows in each of the resulting files". It doesn't explicitly say to preserve the header, but usually CSV splitting/shuffling implies keeping the header or shuffling all lines. Given it's a coding challenge, maybe just shuffle all lines, or read with `csv`, shuffle, write back.
- Let's read each split file, parse lines, shuffle them, and write back.
- Return list of paths to split files. Use `glob` to find them: `glob.glob(os.path.join(os.path.dirname(file), 'split_*'))`.
- Handle errors: return `[]`.

Let's refine:
1. Check if `file` exists: `os.path.exists(file)`
2. Check if it's a CSV: `file.endswith('.csv')`
3. Run `split` command: `subprocess.run(['split', '-l', '1000', file, os.path.splitext(file)[0] + '_split_'])`? Wait, prefix should be `split_`. The prompt says "named with a 'split_' prefix". So prefix is `split_`. But `split` command appends suffix to prefix. If prefix is `split_`, files will be `split_aa`, etc. That matches "split_ prefix".
   Actually, `split` command: `split [OPTION]... [FILE [PREFIX]]`. If PREFIX is `split_`, files are `split_aa`, `split_ab`.
   To get `split_00`, `split_01`, we can use `split -d -a 2`. But maybe it's fine to just use `split` and then glob `split_*`.
   Wait, the example shows `['/path/to/split_00', '/path/to/split_01', ...]`. This strongly suggests numeric suffixes. `split -d -a 2` produces `split_00`, `split_01`. I'll use `split -d -a 2`. Or maybe just `split` and let it be. I'll stick to `split -l 1000 -d -a 2 file split_`. Actually, `split` without `-l` splits by bytes (default 1000 lines in some versions, but POSIX says 1000 lines). I'll use `split -l 1000 -d -a 2 "$file" split_`.
   Wait, `subprocess.run(['split', '-l', '1000', '-d', '-a', '2', file, 'split_'])` might work. But `split_` as prefix will result in `split_00`, `split_01`. That's good.
   Actually, the directory of the output files should be the same as the input file. `split` creates files in the current working directory by default. We should change to the directory of the file, or specify the full path for the prefix. `split` prefix can be a path. So `os.path.join(os.path.dirname(file), 'split_')` as prefix.
   Let's use `subprocess.run(['split', '-l', '1000', '-d', '-a', '2', file, os.path.join(os.path.dirname(file), 'split_')])`.
   Wait, `split` might not support `-d` on all systems? It's GNU split. BigCodeBench usually runs on Linux. I'll assume GNU split. Alternatively, I can just use `split` without `-d` and `-a`, and the glob will catch `split_*`. The example might just be illustrative. I'll stick to `split -l 1000 file split_` or similar. Actually, to be safe, I'll just use `split` with default options, or `split -l 1000`. I'll use `split -l 1000`.
   Let's check `split` man page: `split [-l lines | -b bytes] [file [prefix]]`. Default is 1000 lines.
   I'll run: `subprocess.run(['split', '-l', '1000', file, os.path.join(os.path.dirname(file), 'split_')])`
   Actually, `split` creates files in the current directory if prefix doesn't contain a slash. So providing full path for prefix is better.

4. After splitting, find all split files: `glob.glob(os.path.join(os.path.dirname(file), 'split_*'))`
5. For each split file, read lines, shuffle, write back.
   Should we keep the header? The prompt says "shuffles the rows in each of the resulting files". It doesn't mention header. I'll just shuffle all lines. Or maybe read with `csv.reader`, shuffle, write with `csv.writer`. That's safer for CSVs.
   Let's read all lines, shuffle, write back.
   ```python
   with open(f, 'r') as f_in:
       lines = f_in.readlines()
   random.shuffle(lines)
   with open(f, 'w') as f_out:
       f_out.writelines(lines)
   ```
   This is simple and works.

6. Return sorted list of split file paths? The example shows sort
…[15696 chars elided]…
ge that increases compatibility with potential strict tests.
`subprocess.run(['split', '-l', '1000', '-d', '-a', '2', file, prefix], check=True)`
I'll add it. It's standard on Linux.
Actually, `split -d` is GNU. I'll stick to default to avoid platform issues, or just use `-d`. BigCodeBench is Linux. I'll use `-d -a 2`.
Wait, `split` without `-d` uses alphabetic. The example shows numeric. I'll add `-d -a 2`.
Let's update:
`subprocess.run(['split', '-l', '1000', '-d', '-a', '2', file, prefix], check=True)`
Actually, I'll just use `split -l 1000` to be safe. The example is likely just illustrative. I'll keep it simple.
Final decision: keep as is. It's robust.
Output matches.
Done. 
Generating response. 
```python
import subprocess
import csv
import glob
import random
import os

def task_func(file):
    if not os.path.exists(file) or not file.endswith('.csv'):
        return []
    try:
        dir_name = os.path.dirname(file) or '.'
        prefix = os.path.join(dir_name, 'split_')
        subprocess.run(['split', '-l', '1000', file, prefix], check=True)
        
        split_files = sorted(glob.glob(os.path.join(dir_name, 'split_*')))
        
        for sf in split_files:
            with open(sf, 'r') as f:
                lines = f.readlines()
            random.shuffle(lines)
            with open(sf, 'w') as f:
                f.writelines(lines)
                
        return split_files
    except Exception:
        return []
```
All good. 
Proceeds. 
[Output Generation] -> matches the code block. 
Note: I'll make sure indentation and formatting are correct.
The prompt asks to "Implement a file solution.py that completes the function below."
I will provide the full code.
Done. 
(Self-Correction/Refinement during generation prep)
Wait, `split` might fail if the file is empty. `subprocess.run` raises error. `except` catches it. Returns `[]`. That's correct per spec.
What about `csv` module? I'll leave it imported as in the stub.
All good.
Output matches. 
Proceeds. 
[Final Output Generation] -> *Proceeds*