PythonCreator

Creates features with a user-supplied Python script.

Typical Uses

Reading unsupported formats
Prototyping Python format plugins
Tasks where a transformer is not available

How does it work?

The PythonCreator creates features using the Python script supplied, and sends them into the workspace for processing.

The Python script must be in the form of a Python class. The features can be created either in the input() or close() methods.

Features created in the input() method are created before the first reader is processed. Features created in the close() method are created after all reader features have been processed.

Features are created via the FME Objects Python API.

Note Python is a programming language external to FME. For documentation on creating Python scripts, visit The Python Foundation.

Using Python to perform arbitrary operations on features is a powerful aspect of FME Workbench. However, the logic introduced into a workspace is less visible and can therefore be more difficult to maintain than logic built using FME Workbench’s built-in transformers. It is recommended that other transformers be used when possible instead of Python scripts.

Example Class

The example below creates a random number of features, between 0 and 9.

Script Editing

A PythonCreator transformer can call scripts stored in the transformer itself or stored globally for the entire workspace:

To store a Python script with a specific PythonCreator transformer, use the “Python Script” property of the transformer.
To store a Python script globally, click the Advanced Workspace Parameter in the Navigator, and double-click Startup Python Script. Storing scripts globally has the advantage of keeping your Python logic centralized, which makes editing and maintenance easier. This is useful if you want to have multiple PythonCreator transformers throughout your workspace that use the same script. For more information, see Startup and Shutdown Python Scripts in the FME Workbench help.

If you are using extensive Python libraries that you do not want to store inside a workspace: to avoid duplication, you can access .py files on the file system using Python’s import command. In addition to the standard Python module locations, FME will also search the location of the workspace for an imported Python module.

Configuration

Input Ports

None

Output Ports

Parameters

General

Class to Process Features

The name of the Python Class within the script that PythonCreator will use to begin execution. For the above example, set this parameter to FeatureCreator.

Python Script

This is the Python script to be executed. If the Python script is stored as the Startup Python Script for the workspace (as described above in Script Editing) you can leave this parameter blank.

Attributes to Expose

Exposes attributes so they can be used elsewhere in the workspace.

Attribute names may be entered directly or provided in the Enter Values for Attributes to Expose dialog accessed via the ellipsis button, where data type may also be specified.

For more information on exposed and unexposed attributes, see Understanding Feature Types and Attributes.

Used to expose any attributes that are created by the Python script being executed so they can be used by other transformers.

Editing Transformer Parameters

Using a set of menu options, transformer parameters can be assigned by referencing other elements in the workspace. More advanced functions, such as an advanced editor and an arithmetic editor, are also available in some transformers. To access a menu of these options, click beside the applicable parameter. For more information, see Transformer Parameter Menu Options.

Defining Values

There are several ways to define a value for use in a Transformer. The simplest is to simply type in a value or string, which can include functions of various types such as attribute references, math and string functions, and workspace parameters. There are a number of tools and shortcuts that can assist in constructing values, generally available from the drop-down context menu adjacent to the value field.

How to Set Parameter Values

Using the Text Editor

The Text Editor provides a convenient way to construct text strings (including regular expressions) from various data sources, such as attributes, parameters, and constants, where the result is used directly inside a parameter.

Text Editor

Using the Arithmetic Editor

The Arithmetic Editor provides a convenient way to construct math expressions from various data sources, such as attributes, parameters, and feature functions, where the result is used directly inside a parameter.

Arithmetic Editor

Conditional Values

Set values depending on one or more test conditions that either pass or fail.

Parameter Condition Definition Dialog

Content

Expressions and strings can include a number of functions, characters, parameters, and more.

When setting values - whether entered directly in a parameter or constructed using one of the editors - strings and expressions containing String, Math, Date/Time or FME Feature Functions will have those functions evaluated. Therefore, the names of these functions (in the form @<function_name>) should not be used as literal string values.

Content Types

String Functions	These functions manipulate and format strings.
Special Characters	A set of control characters is available in the Text Editor.
Math Functions	Math functions are available in both editors.
Date/Time Functions	Date and time functions are available in the Text Editor.
Math Operators	These operators are available in the Arithmetic Editor.
FME Feature Functions	These return primarily feature-specific values.
FME Parameters	FME and workspace-specific parameters may be used.
Creating and Modifying User Parameters	Create your own editable parameters.

Dialog Options - Tables

Transformers with table-style parameters have additional tools for populating and manipulating values.

Table Tools

Row Reordering

Enabled once you have clicked on a row item. Choices include:

Add a row
Remove a row
Move current row up one
Move current row down one
Move current row to top
Move current row to bottom

Cut, Copy, and Paste

Enabled once you have clicked on a row item. Choices include:

Cut a row - delete and copy to clipboard
Copy a row to the clipboard
Paste a row from the clipboard

Cut, copy, and paste may be used within a transformer, or between transformers.

Filter

Start typing a string, and the matrix will only display rows matching those characters. Searches all columns. This only affects the display of attributes within the transformer - it does not alter which attributes are output.

Import

Import populates the table with a set of new attributes read from a dataset. Specific application varies between transformers.

Reset/Refresh

Generally resets the table to its initial state, and may provide additional options to remove invalid entries. Behavior varies between transformers.

Note: Not all tools are available in all transformers.

Reference

Processing Behavior	Feature-Based or Group-Based, conditional on Python script
Feature Holding	Conditional on Python script
Dependencies	Specifying a Python Interpreter An FME installation includes a Python version 2.7 and Python version 3.5 interpreter. The default Python interpreter used for Python processing is the Python 2.7 interpreter. The FME Objects Python API supports Python 2.7, Python 3.4, and Python 3.5. The Python interpreter used by FME to execute Python scripts is controlled by the Python Compatibility workspace parameter and the Preferred Python Interpreter setting under Tools > FME Options > Translation. Python Compatibility specifies the version of Python with which Python scripts are compatible. FME loads the Preferred Python Interpreter if it is compatible with the Python Compatibility. If not, FME loads an appropriate Python interpreter matching Python Compatibility. For more information, see the FME Workbench help. Installing Python Packages If you would like to install a third-party package for use by Python in FME, see Installing Python Packages to FME Form in the FME Workbench help.
Aliases
History

FME Community

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Examples may contain information licensed under the Open Government Licence – Vancouver and/or the Open Government Licence – Canada.