path: root/src/arrow/python/pyarrow/tests/util.py

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"""
Utility functions for testing
"""

import contextlib
import decimal
import gc
import numpy as np
import os
import random
import signal
import string
import subprocess
import sys

import pytest

import pyarrow as pa
import pyarrow.fs


def randsign():
    """Randomly choose either 1 or -1.

    Returns
    -------
    sign : int
    """
    return random.choice((-1, 1))


@contextlib.contextmanager
def random_seed(seed):
    """Set the random seed inside of a context manager.

    Parameters
    ----------
    seed : int
        The seed to set

    Notes
    -----
    This function is useful when you want to set a random seed but not affect
    the random state of other functions using the random module.
    """
    original_state = random.getstate()
    random.seed(seed)
    try:
        yield
    finally:
        random.setstate(original_state)


def randdecimal(precision, scale):
    """Generate a random decimal value with specified precision and scale.

    Parameters
    ----------
    precision : int
        The maximum number of digits to generate. Must be an integer between 1
        and 38 inclusive.
    scale : int
        The maximum number of digits following the decimal point.  Must be an
        integer greater than or equal to 0.

    Returns
    -------
    decimal_value : decimal.Decimal
        A random decimal.Decimal object with the specified precision and scale.
    """
    assert 1 <= precision <= 38, 'precision must be between 1 and 38 inclusive'
    if scale < 0:
        raise ValueError(
            'randdecimal does not yet support generating decimals with '
            'negative scale'
        )
    max_whole_value = 10 ** (precision - scale) - 1
    whole = random.randint(-max_whole_value, max_whole_value)

    if not scale:
        return decimal.Decimal(whole)

    max_fractional_value = 10 ** scale - 1
    fractional = random.randint(0, max_fractional_value)

    return decimal.Decimal(
        '{}.{}'.format(whole, str(fractional).rjust(scale, '0'))
    )


def random_ascii(length):
    return bytes(np.random.randint(65, 123, size=length, dtype='i1'))


def rands(nchars):
    """
    Generate one random string.
    """
    RANDS_CHARS = np.array(
        list(string.ascii_letters + string.digits), dtype=(np.str_, 1))
    return "".join(np.random.choice(RANDS_CHARS, nchars))


def make_dataframe():
    import pandas as pd

    N = 30
    df = pd.DataFrame(
        {col: np.random.randn(N) for col in string.ascii_uppercase[:4]},
        index=pd.Index([rands(10) for _ in range(N)])
    )
    return df


def memory_leak_check(f, metric='rss', threshold=1 << 17, iterations=10,
                      check_interval=1):
    """
    Execute the function and try to detect a clear memory leak either internal
    to Arrow or caused by a reference counting problem in the Python binding
    implementation. Raises exception if a leak detected

    Parameters
    ----------
    f : callable
        Function to invoke on each iteration
    metric : {'rss', 'vms', 'shared'}, default 'rss'
        Attribute of psutil.Process.memory_info to use for determining current
        memory use
    threshold : int, default 128K
        Threshold in number of bytes to consider a leak
    iterations : int, default 10
        Total number of invocations of f
    check_interval : int, default 1
        Number of invocations of f in between each memory use check
    """
    import psutil
    proc = psutil.Process()

    def _get_use():
        gc.collect()
        return getattr(proc.memory_info(), metric)

    baseline_use = _get_use()

    def _leak_check():
        current_use = _get_use()
        if current_use - baseline_use > threshold:
            raise Exception("Memory leak detected. "
                            "Departure from baseline {} after {} iterations"
                            .format(current_use - baseline_use, i))

    for i in range(iterations):
        f()
        if i % check_interval == 0:
            _leak_check()


def get_modified_env_with_pythonpath():
    # Prepend pyarrow root directory to PYTHONPATH
    env = os.environ.copy()
    existing_pythonpath = env.get('PYTHONPATH', '')

    module_path = os.path.abspath(
        os.path.dirname(os.path.dirname(pa.__file__)))

    if existing_pythonpath:
        new_pythonpath = os.pathsep.join((module_path, existing_pythonpath))
    else:
        new_pythonpath = module_path
    env['PYTHONPATH'] = new_pythonpath
    return env


def invoke_script(script_name, *args):
    subprocess_env = get_modified_env_with_pythonpath()

    dir_path = os.path.dirname(os.path.realpath(__file__))
    python_file = os.path.join(dir_path, script_name)

    cmd = [sys.executable, python_file]
    cmd.extend(args)

    subprocess.check_call(cmd, env=subprocess_env)


@contextlib.contextmanager
def changed_environ(name, value):
    """
    Temporarily set environment variable *name* to *value*.
    """
    orig_value = os.environ.get(name)
    os.environ[name] = value
    try:
        yield
    finally:
        if orig_value is None:
            del os.environ[name]
        else:
            os.environ[name] = orig_value


@contextlib.contextmanager
def change_cwd(path):
    curdir = os.getcwd()
    os.chdir(str(path))
    try:
        yield
    finally:
        os.chdir(curdir)


@contextlib.contextmanager
def disabled_gc():
    gc.disable()
    try:
        yield
    finally:
        gc.enable()


def _filesystem_uri(path):
    # URIs on Windows must follow 'file:///C:...' or 'file:/C:...' patterns.
    if os.name == 'nt':
        uri = 'file:///{}'.format(path)
    else:
        uri = 'file://{}'.format(path)
    return uri


class FSProtocolClass:
    def __init__(self, path):
        self._path = path

    def __fspath__(self):
        return str(self._path)


class ProxyHandler(pyarrow.fs.FileSystemHandler):
    """
    A dataset handler that proxies to an underlying filesystem.  Useful
    to partially wrap an existing filesystem with partial changes.
    """

    def __init__(self, fs):
        self._fs = fs

    def __eq__(self, other):
        if isinstance(other, ProxyHandler):
            return self._fs == other._fs
        return NotImplemented

    def __ne__(self, other):
        if isinstance(other, ProxyHandler):
            return self._fs != other._fs
        return NotImplemented

    def get_type_name(self):
        return "proxy::" + self._fs.type_name

    def normalize_path(self, path):
        return self._fs.normalize_path(path)

    def get_file_info(self, paths):
        return self._fs.get_file_info(paths)

    def get_file_info_selector(self, selector):
        return self._fs.get_file_info(selector)

    def create_dir(self, path, recursive):
        return self._fs.create_dir(path, recursive=recursive)

    def delete_dir(self, path):
        return self._fs.delete_dir(path)

    def delete_dir_contents(self, path):
        return self._fs.delete_dir_contents(path)

    def delete_root_dir_contents(self):
        return self._fs.delete_dir_contents("", accept_root_dir=True)

    def delete_file(self, path):
        return self._fs.delete_file(path)

    def move(self, src, dest):
        return self._fs.move(src, dest)

    def copy_file(self, src, dest):
        return self._fs.copy_file(src, dest)

    def open_input_stream(self, path):
        return self._fs.open_input_stream(path)

    def open_input_file(self, path):
        return self._fs.open_input_file(path)

    def open_output_stream(self, path, metadata):
        return self._fs.open_output_stream(path, metadata=metadata)

    def open_append_stream(self, path, metadata):
        return self._fs.open_append_stream(path, metadata=metadata)


def get_raise_signal():
    if sys.version_info >= (3, 8):
        return signal.raise_signal
    elif os.name == 'nt':
        # On Windows, os.kill() doesn't actually send a signal,
        # it just terminates the process with the given exit code.
        pytest.skip("test requires Python 3.8+ on Windows")
    else:
        # On Unix, emulate raise_signal() with os.kill().
        def raise_signal(signum):
            os.kill(os.getpid(), signum)
        return raise_signal