Creates features with a user-supplied Python script.
- 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 Workbench. However, the logic introduced into a workspace is less visible and can therefore be more difficult to maintain than logic built using Workbench’s built-in transformers. It is recommended that other transformers be used when possible instead of Python scripts.
The example below creates a random number of features, between 0 and 9.
self.number = random.random()
def input(self, feature):
for i in range(1, int(self.number*10)):
feature = fmeobjects.FMEFeature()
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.
Features created by the Python script.
|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 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.
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.
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.
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.
Set values depending on one or more test conditions that either pass or fail.
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.
|These functions manipulate and format strings.|
|A set of control characters is available in the Text Editor.|
|Math functions are available in both editors.|
|Date/Time Functions||Date and time functions are available in the Text Editor.|
|These operators are available in the Arithmetic Editor.|
|These return primarily feature-specific values.|
|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.
Enabled once you have clicked on a row item. Choices include:
Cut, Copy, and Paste
Enabled once you have clicked on a row item. Choices include:
Cut, copy, and paste may be used within a transformer, or between transformers.
|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 populates the table with a set of new attributes read from a dataset. Specific application varies between transformers.|
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.
Conditional on Python script
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.
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Examples may contain information licensed under the Open Government Licence – Vancouver and/or the Open Government Licence – Canada.