Version 2.4

17 March 2023

feature Generation of YAML configuration for CLI synthesis

Using -g option a default YAML configuration file can be generated for use in command line synthesis. See Command Line Interface for the complete guide.

feature Ability to supply and overwrite columns when synthesizing event data

When synthesizing event data, it is now possible to supply a DataFrame containing columns that should be used to overwrite the columns in the synthesized data. For example:

#    a    b
# 0  1  yes
# 1  2  yes
# 2  1   no

#         time  a    b    c
# 0 2023-06-01  1  yes  3.2
# 1 2023-06-02  2  yes -1.1
# 2 2023-06-06  1   no  0.3

As the data is synthesized, the columns in df_overwrite are used to constrain the generative model output. This can be used to ensure that specific columns of the synthetic data are identical to their original counterparts. (See in the above example columns a and b are maintained in the output.)

enhancement Command line synthesis YAML configuration expanded

The parameters that can be configured in YAML when using the synthesized command line synthesis have been expanded. YAML configuration files will now be validated against a default schema, ensuring that the appropriate keywords and values dtypes have been provided. See YAML Configuration for the complete guide.

If a parameter is specified in the YAML config and also as a command line argument, then the command line argument will take priority.

breaking change Names of Privacy Masks have changed

The names of the Privacy Masks has changed:











In addition, the name of the methods of MaskingFactory have also been changed:









breaking change Format of arguments to MaskingFactory have changed

When using the create_masks method of MaskingFactory (previously known as the create_transformers method of the ` MaskingTransformerFactory`, see above) the format of the config argument has been changed. All arguments are now provided in a dictionary, where previously the | separator was used between the masking technique and associated value:



config = {
config = {
  "rounding": [
      {"name": "Age", "nbins": None},
      {"name": "Income", "nbins": "3"}
  "format_preserving": [
      {"name": "Code", "pattern" : "\d{3}"}
  "nan": [
      {"name" : "Password"}

See the Privacy Masks documentation for more details.

breaking change API of MaskingTransformerFactory has changed

To create a set of masking transformers using the create_transformers method of the MaskingTransformerFactory the DataFrame to be masked now needs to be supplied as an argument,



masking_transformers = (
masking_transformers = (
    .create_transformers(df, config)

bug DataFrameTransformer returned by MaskingTransformerFactory not returning all columns

When calling transform on the DataFrameTransformer object returned by the create_transformers method of MaskingTransformerFactory, only the masked columns were returned. This bug has now been fixed such that all columns in the DataFrame passed to the transform method are now returned.

bug Incorrect Event Synthesis for datasets with almost regular events

Datasets that only have a few unique values when diffing the time_index (i.e., df["time_index"].diff().nunique()) were being incorrectly synthesized. In these circumstances, all events for each entity were being synthesized to occur at the same time. This bug has now been fixed.

Version 2.3

19 December 2022

Version 2.3 of the python SDK. (Wheel archive ).

enhancement Support for Python 3.10

Synthesized now supports python 3.7, 3.8, 3.9, and 3.10 on Windows, MacOS and Linux.

enhancement Support for ARM64 on MacOS

Specific wheel files for ARM64 architectures (such as the Apple M1 chips) are now built and uploaded to PyPI by default for python 3.8, 3.9, and 3.10.

bug pip install dependency issue

A bug causing pip install synthesized from PyPI to install the wrong version of a dependency has been fixed.

Version 2.2

24 November 2022

Version 2.2 of the python SDK. (Wheel archive ).

enhancement Dense Layers with Batch Normalisation don’t need Bias

Dense Layers can be described by

where are the weights and biases of the layer and is the activation function.

When batch normalisation is used, it’s applied before the activation function and normalises by the mean and standard deviation of the batch. Batch normalisation also scales the output with two learned parameters and , i.e.

The scaled is then passed to the activation function .

The expectation value of over a given batch, , is given by

Substituting this and the first equation in for the expression for gives

where the bias from the dense layer cancels

meaning the bias for a dense layer doesn’t affect the output when batch normalisation is used. Instead, the term acts as a bias.

This means that the dense layers with batch normalisation have the unnecessary overhead of learning a bias which will take more time to train and result in a larger overall model. This redundancy was addressed in this enhancement.

enhancement Use value_counts instead of Moving Average in CategoricalValue

Instead of calculating the moving average of categorical counts during training (which has fluctuations) we can get the categorical value counts once before training begins and set those values as constants during training.

This has three benefits:

  • It is faster to train. as we don’t calculate moving average.

  • It is more accurate as the counts from the entire dataframe aren’t just an estimate of the frequencies.

  • It allows us to JIT compile the model in tensorflow. The moving average layer was the only TensorFlow layer that could not be JIT compiled.

enhancement TensorFlow matrix multiplication speed-up

The performance of learning and synthesizing has been improved by utilizing TensorFlows' compilation optimizations for matrix multiplication. This optimization requires configuration changes and improves the HighDimSynthesizer, TimeSeriesSynthesizer and EventSynthesizer.

feature TimeSeriesSynthesizer for regular time series and EventSynthesizer for event-based synthesis

In addition to tabular data Synthesized now supports two more forms of data:

  • Time series: Synthesize regularly spaced time-series data.

  • Event data: Create synthetic event-based data.

import pandas as pd
from synthesized import TimeSeriesSynthesizer

df = pd.read_csv(...)

synth = TimeSeriesSynthesizer(
), epochs=15, steps_per_epoch=5000)


feature Add .from_df() constructor to HighDimSynthesizer

As a shortcut to quickly create a HighDimSynthesizer from a pandas.DataFrame, the .from_df() constructor has been added.

with MetaExtractor

with .from_df()

df = pd.read_csv(...)
df_meta = MetaExtractor.extract(df)
synth = HighDimSynthesizer(df_meta)
df = pd.read_csv(...)
synth = HighDimSynthesizer.from_df(df)

feature Optionally use StandardScalar instead of QuantileTransformer

Previously, the QuantileTransformer was always used when training any model. However, this is an especially non-linear process and can negatively impact a model’s ability to impute nan values. Now, it is possible to configure the ContinuousTransformer to optionally use a StandardScalar instead of the QuantileTransformer.

synth = HighDimSynthesizer(df_meta, config=HighDimConfig(quantile=False))

feature Optionally show the training metrics with the progress callbacks

It is now possible to set 3 different levels of verbosity (0, 1, 2) for the training progress of HighDimSynthesizer

synth.learn(df, verbose=0)

bug Histogram probabilities do not sum to 1

When synthesizing some forms of categorical data, an error was thrown due to the Histogram module not pulling through the correct probabilities for categories to appear. This has now been fixed.

bug Assessor metric matrices 2x2 plot formatting issue

When small Assessor metric matrices were plotted the formatting was incorrect. This has been fixed.



Old metric matrix plot.
New metric matrix plot.

bug Synthesis of integers sometimes gives floats

When using the DataImputer missing values in integer dtype columns were sometimes incorrectly imputed as floats. This has been fixed in this version.

Version 2.1

5 August 2022

Version 2.1 of the python SDK. (Wheel archive ).

feature PyPI integration

Synthesized is now available for install via PyPI! See Installation.

feature 30 Day Trial Licence

Synthesized now supports a free 30 day trial licence which can be requested on import of synthesized or by running the synth-validate cli command. See Setting the licence key.

feature JSON synthesis supported

The SDK now has the ability to support and synthesize JSON column types.

Version 2.0

15 July 2022

Version 2.0 of the python SDK. (Wheel archive ).

enhancement Internal Framework Rebuild

With v2.0 the underlying framework of the SDK has been rebuilt, making it easier to extend in preparation for a wealth of new features planned for upcoming versions. The internal restructure paves the way for more native integration with a host of datasources, as well as providing some slight performance improvements with the majority of supported datatypes.

enhancement Documentation

The documentation pages have been revamped and improved.

feature YAML configuration for command line synthesis

Previously in v1.10 a command line synthesis feature was added. Moving towards greater integrations with CICD and process flows, YAML files can also be used to specify synthesis feature options. This means all the Synthesized manipulations can be specified in an easy-to-write YAML file and passed to the synthesize command above, allowing developers, devops engineers, data engineers, and the like to write synthetic data specifications in clear YAML and run it without having to touch a line of python.

Specify a config file using the -c or --config flags followed by the name of the config file. i.e.:

$ synthesize -h
usage: synthesize [-h] [-c config.yaml] [-n N] [-s steps] [-o out_file] file

Create a synthetic copy of a given csv file.

positional arguments:
  file                  The path to the original csv file.

optional arguments:
  -h, --help            show this help message and exit
  -c config.yaml, --config config.yaml
                        Path to an optional yaml config file.
  -n N                  The number of rows to synthesize. (default: The same
                        number as the original data)
  -s steps              The number of training steps. (default: Use learning
                        manager instead)
  -o out_file, --output out_file
                        The destination path for the synthesized data.
                        (default: outputs to stdout)

The YAML file structure should look something like:

    type: person
      fullname: name
      gender: sex
      email: mail
      username: username

    type: date_time
    date_format: '%m/%y'
    type: formatted_string
    pattern: '\d{3}-\d{2}-\d{4}'

breaking change Annotations

The config required for the Annotation files has been simplified. Where previously the input arguments ended in _label, now the _label ending has been removed so just the keywords are required. Below is an example with the Person annotations, but the change has been made for all annotations.



person = Person(
person = Person(

breaking change Produce NaNs

The default value for produce_nans has been changed from False to True. Previously, the default behaviour of the SDK was to impute NaNs in the output data. After some consideration, it was decided that the default behaviour should be to most accurately represent the raw input data, NaNs included, and that imputation of NaNs is a special feature of the SDK that can be turned on at will.

To ensure NaNs are imputed in the output data in v2.0, produce_nans must now be manually set to True during synthesis.




# Previously, to produce NaNs - specify parameter
synth.synthesize(1000, produce_nans=True)

# Previously, NaNs imputed by default

# Now, produce NaNs by default

# Now, to impute NaNs - specify parameter
synth.synthesize(1000, produce_nans=False)

bug String nulls not cast correctly

A bug causing nulls in String category columns not to be cast properly has been fixed.

bug NaN associations with non-NaN columns

If NaN associations were attempted on columns with no NaNs present, previously an error occurred. A fix has been added to inform the user there are no NaNs in the specified column and to continue the Association without the non-NaN column.

Version 1.11

24 April 2022

Version 1.11 of the python SDK. (Wheel archive ).

bug Timedelta datatype generation

A bug causing Timedelta and NaT data generation to raise an exception in some situations has been fixed.

bug Person annotation causing error

A bug causing the Person annotation to raise an exception has been fixed.

Version 1.10

14 April 2022

Version 1.10 of the python SDK. (Wheel archive ).

feature Simple time-series synthesis

We’ve been working hard to add more advanced time-series capabilities to the SDK. This release contains the initial framework for synthesizing and assessing time-series data.

Setting DataFrame indices

MetaExtractor.extract now has two optional arguments to specify which columns are the ID & time indices.

import pandas as pd
from synthesized import MetaExtractor
df = pd.read_csv("")
df_meta = MetaExtractor.extract(df, id_index="Name", time_index="date")

The index of the DataFrame is a pd.MultiIndex and allows the DataFrame to be neatly reformatted into a panel which cross sections can be taken from:


Time-series plots

In order to plot and compare different time-series values for different entities, we can plot time series with four different options of ShareSetting.

  1. Entities share the same plot ShareSetting.PLOT

  2. Entities have different plots but share the same x- and y-axis. ShareSetting.AXIS

  3. Entities have different plots but share the same x-axis. ShareSetting.X_AXIS

  4. No sharing. Each plot is independent. ShareSetting.NONE

For example:

# Full script
import pandas as pd
from synthesized import MetaExtractor
from synthesized.testing.plotting.series import plot_multi_index_dataframes, ShareSetting

# Account IDs to plot
categories_to_plot = [2378,  576,  704, 3818, 1972]

# Columns to plot
continuous_ids = ["balance", "index"]
categorical_ids = ["bank", "k_symbol"]
ids = continuous_ids + categorical_ids

# Load data
df_categorical = pd.read_csv("")
# Reduce data down to smaller volume for processing
df_categorical = df_categorical[df_categorical.type != "VYBER"]
df_categorical = df_categorical[ids + ["account_id", "date"]]

# Extract metadata
df_categorical_meta = MetaExtractor.extract(df_categorical, id_index="account_id", time_index="date")

# Plot dataframe
plot_multi_index_dataframes(df_categorical, df_categorical_meta, columns_to_plot=ids, categories_to_group_plots=categories_to_plot, share_setting=ShareSetting.AXES)
Plot timeseries data with categories.

Synthesizing time-series with Regression Models

You can now create synthetic data using the Regression model.

feature Synthesize from the command line

Calling synthesize after installing the SDK package with pip will allow users to create synthetic copies of csv data files from the command line.


$ synthesize -h
usage: synthesize [-h] [-n N] [-s steps] [-o out_file] file

Create a synthetic copy of a given csv file.

positional arguments:
file                  The path to the original csv file.

optional arguments:
-h, --help            show this help message and exit
-n N                  The number of rows to synthesize. (default: The same number as the
                        original data)
-s steps              The number of training steps. (default: Use learning manager instead)
-o out_file, --output out_file
                        The destination path for the synthesized data. (default: outputs to

bug AttributeInferenceAttackML causes OOM issues with large categorical columns

The :class:`AttributeInferenceAttackML` has been optimized to avoid allocating excessively large amounts of memory when handling categorical columns. This resolves an issue where relatively small datasets would cause out of memory (OOM) issues.

bug Assessor doesn’t work with null columns

Previously, the :class:`Assessor` would fail when attempting to plot a dataset containing a completely empty column (NaNs only). This has been resolved.

The Assessor now returns an empty plot containing the text "NaN" for these columns.

bug Support FormatPreservingTransformer with MaskingTransformerFactory

Previously, there was no way to create synthesized.privacy.FormatPreservingTransformer using synthesized.privacy.MaskingTransformerFactory. Attempting to do so would raise an error:

ValueError: Given masking technique 'format_preserving|[abc]{3}' for column '{column}' not supported

You can now correctly create the Transformer with the MaskingDataFactory. For example:

mtf = MaskingTransformerFactory()
df_transformer = mtf.create_transformers({"col1": r"format_preserving|\d{3}"})
fp_transformer = dfm_trans._transformers[0]
assert isinstance(fp_transformer, FormatPreservingTransformer)  # True

Version 1.9

6 Feb 2022

Version 1.9 of the python SDK. (Wheel archive ).

feature Command to validate installation

After running pip install, you can now use the terminal command synth-validate to confirm the SDK is working.

This command will log licence info to the terminal and attempt to synthesize a small dataset. It should take under 1 minute to complete.

enhancement Support python 3.9

Synthesized now supports python 3.6, 3.7, 3.8, and 3.9 on Windows, MacOS and Linux. Wheels are built and tested for all 12 versions.