whylabs-datasketches 2.0.0b7

A wrapper for the C++ Datasketches library

# Python Wrapper for Datasketches

## Installation

The release files do not include the needed python binding library ([pybind11](https://github.com/pybind/pybind11)). If building from a relase package, you must ensure that the pybind11 directory points to a local copy of pybind11.

An official pypi build is eventually planned but not yet available.

If you instead want to take a (possibly ill-advised) gamble on the current state of the master branch being useable, you can run: `pip install git+https://github.com/apache/incubator-datasketches-cpp.git`

## Developer Instructions

### Building

When cloning the source repository, you should include the pybind11 submodule with the –recursive option to the clone command: ` git clone --recursive https://github.com/apache/incubator-datasketches-cpp.git cd incubator-datasketches-cpp python -m pip install --upgrade pip setuptools wheel numpy python setup.py build `

If you cloned without –recursive, you can add the submodule post-checkout using git submodule update –init –recursive.

### Installing

Assuming you have already checked out the library and any dependent submodules, install by simply replacing the lsat line of the build command with python setup.py install.

### Unit tests

The python tests are run with tox. To ensure you have all the needed packages, from the package base directory run: ` python -m pip install --upgrade pip setuptools wheel numpy tox tox `

## Usage

Having installed the library, loading the Datasketches library in Python is simple: import datasketches.

## Available Sketch Classes

• KLL

  • kll_ints_sketch

  • kll_floats_sketch

• Frequent Items

  • frequent_strings_sketch

  • Error types are frequent_items_error_type.{NO_FALSE_NEGATIVES | NO_FALSE_POSITIVES}

• Theta

  • update_theta_sketch

  • compact_theta_sketch (cannot be instantiated directly)

  • theta_union

  • theta_intersection

  • theta_a_not_b

• HLL

  • hll_sketch

  • hll_union

  • Target HLL types are tgt_hll_type.{HLL_4 | HLL_6 | HLL_8}

• CPC

  • cpc_sketch

  • cpc_union

• VarOpt Sampling

  • var_opt_sketch

  • var_opt_union

## Known Differences from C++

The Python API largely mirrors the C++ API, with a few minor exceptions: The primary known differences are that Python on modern platforms does not support unsigned integer values or numeric values with fewer than 64 bits. As a result, you may not be able to produce identical sketches from within Python as you can with Java and C++. Loading those sketches after they have been serialized from another language will work as expected.

We have also removed reliance on a builder class for theta sketches as Python allows named arguments to the constructor, not strictly positional arguments.