Question

Python Shutdown Best Practise - Global Variables + Published Parameters

  • 14 December 2012
  • 12 replies
  • 24 views
moberdries
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Badge +3

I am trying to create a Python FME shutdown script.  I need it to reference two types of variable - (1) a static variable; and (2) a variable whose value is only known at FME runtime.

 

 

Option (1) I can ebale through a Published Parameter and reference it in my shutdown script as $FME_MacroValues(myParam)

 

 

Option (2) is trickier.  I tried to use a VariableSetter transformer in the workbench but the shutdown script did not seem to recognise the variable.  I also tried to create a dummy published parameter and reset its value at runtime using the VariableSetter again, but the shutdown script only recognised it default value, not its runtime value.

 

 

Do I need to set a global variable first in a startup script; modfiy it at runtime; and the use it in a shutdown script - not quite sure on the syntax if this is the best practise here?

 

 

So how are you meant to expose a global variable and/or a published parameter that gets updated at FME runtime in a python shutdown script?  If someone can provide some sample python syntax that would really help me out.

Regards

 

Mike

12 replies

takashi
Rank
Userlevel 2
Badge +17
Hi,   PythonCaller might be available.   # Startup # declare a global variable and set default value myParam = 'default value'   # PythonCaller # modify value in the function def modifyMyParam(feature):     global myParam     myParam = 'modified value'   # Shutdown # refer the global variable print myParam  
fmelizard
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Userlevel 3
Badge +13
takashi's approach is a good one - but in fact you don't need to declare the variable in a start-up script.  Here is a workspace example where we set the count attribute with a PythonCaller and get it in a Shutdown script: 

 

https://dl.dropbox.com/u/2377887/GetCounter.fmw
takashi
Rank
Userlevel 2
Badge +17
Hello Ken, Thanks your supplements. If saying a little more strictly, when the following conditions are satisfied, it's sure that declaration of the global variable in startup script is not essential. - Default value of the variable is unnecessary. - It's guaranteed that the function in which the global variable was declared is called at least 1 time when running the workspace.  
K
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Apparently the workspace link I posted above is broken.  Below is the code you can use to make an attribute value accessible in a Shutdown script. (Note: you can use the same method to make a Parameter Value  accessible by using a ParameterFetcher transformer first to convert your parmater value into an attribute value)

 

 

Assuming you have an attribute called _count

 

 

1. PythonCaller Tranformer
  • Set the parameter "Class or Function " to processFeature
  • Then enter this script
import fmeobjects

 

 

def processFeature(feature):

 

  global MyCounter  

 

  MyCounter = feature.getAttribute('_count')  

 

  pass

 

2. In your Shutodown Script

 

 

import fmeobjects

 

MyCounter = str(MyCounter)

 

print MyCounter

 

G
Badge

I need some suggestions on how to implement the dataset format parameter in my shutdown script. 

My current shutdown script below has a hardcoded html path/filename and I'd like to use the FeatureWriter dataset parameter as url to my shutdown script.

import fme
import fmeobjects
import webbrowser
new = 2 # open in a new tab, if possible

# open an HTML file on my own (Windows) computer
url = "file://///H:/2016/DGN_Conversions/Solution/output/HelloWorld.html"
webbrowser.open(url,new=new)

I added a pythonCaller after my featureWriter with the script below

print MyFile outputs 

 

\\alxapfs23\RSALVALE$\2016\DGN_Conversions\Solution\output\HelloWorld.html
import fme
import fmeobjects
# Template Function interface:
# When using this function, make sure its name is set as the value of
# the 'Class or Function to Process Features' transformer parameter
def processFeature(feature):
    global MyFile  
    MyFile = feature.getAttribute('_dataset')
    print MyFile
    pass
I get this error message from FME:  FME_END_PYTHON: evaluating python script from string...

2016-07-21 10:57:03|   1.3|  0.0|INFORM|END - ProcessID: 13812, peak process memory usage: 70520 kB, current process memory usage: 70416 kB







Python Exception <TypeError>: unsupported operand type(s) for &: 'str' and 'str'




Traceback (most recent call last):

  File "<string>", line 12, in <module>

TypeError: unsupported operand type(s) for &: 'str' and 'str'




Error executing string
G
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@ken and @takashi do you have any suggestions? Thanks!

M
Badge +2

@geospatiallover

This works for me:

import fmeobjectsimport webbrowser# Template Function interface:def popup(feature):    MyFile = feature.getAttribute('_dataset')    print MyFile    new = 2 # open in a new tab, if possible    # open an HTML file on my own (Windows) computer    url = MyFile    webbrowser.open(url,new=new)

Here's it running in a test Workspace:

htmlbrowserpopup.fmw

david_r
Rank
Userlevel 4

I need some suggestions on how to implement the dataset format parameter in my shutdown script. 

My current shutdown script below has a hardcoded html path/filename and I'd like to use the FeatureWriter dataset parameter as url to my shutdown script.

import fme
import fmeobjects
import webbrowser
new = 2 # open in a new tab, if possible

# open an HTML file on my own (Windows) computer
url = "file://///H:/2016/DGN_Conversions/Solution/output/HelloWorld.html"
webbrowser.open(url,new=new)

I added a pythonCaller after my featureWriter with the script below

print MyFile outputs 

 

\\alxapfs23\RSALVALE$\2016\DGN_Conversions\Solution\output\HelloWorld.html
import fme
import fmeobjects
# Template Function interface:
# When using this function, make sure its name is set as the value of
# the 'Class or Function to Process Features' transformer parameter
def processFeature(feature):
    global MyFile  
    MyFile = feature.getAttribute('_dataset')
    print MyFile
    pass
I get this error message from FME:  FME_END_PYTHON: evaluating python script from string...

2016-07-21 10:57:03|   1.3|  0.0|INFORM|END - ProcessID: 13812, peak process memory usage: 70520 kB, current process memory usage: 70416 kB







Python Exception <TypeError>: unsupported operand type(s) for &: 'str' and 'str'




Traceback (most recent call last):

  File "<string>", line 12, in <module>

TypeError: unsupported operand type(s) for &: 'str' and 'str'




Error executing string

Can you show us your shutdown script?

G
Badge

@geospatiallover

This works for me:

import fmeobjectsimport webbrowser# Template Function interface:def popup(feature):    MyFile = feature.getAttribute('_dataset')    print MyFile    new = 2 # open in a new tab, if possible    # open an HTML file on my own (Windows) computer    url = MyFile    webbrowser.open(url,new=new)

Here's it running in a test Workspace:

htmlbrowserpopup.fmw

Thanks and I tested your FMW and it worked as suggested. 

fmelizard
Rank
Userlevel 3
Badge +13

Hello @geospatiallover - Please try publishing the Dataset Value as a parameter in the FeatureWriter and then access this parameter in the python shutdown script using something like: SourceDataset = FME_MacroValues['URL'] - where 'URL' is the published parameter name.

G
Badge

@CandaceAtSafe, I got your email and sample fmw and it worked for me. Thanks!

helmoet
Badge +2

Hi, On the issue of passing runtime data from FME Workspace to shutdown script this one, bit old fashioned may be, however works for me [FME 2015], might not work on all platforms and might be a bit dirty:

I use a Creator and a PythonCaller executing the following script that creates an environment variable:

import fme
import fmeobjects
import os

# Template Function interface:
def FeatureProcessor(feature):  
  os.environ['A_VAR'] = 'My value'
  print os.environ['A_VAR']  
  pass

The shutdown python script just references the Env var created in the PythonCaller script:

import os

print 'THIS IS SHUTDOWN\n'
print os.environ['A_VAR']

Here is the result:

.
.
.
.
Translation was SUCCESSFUL with 0 warning(s) (0 feature(s) output)
FME Session Duration: 1.2 seconds. (CPU: 0.2s user, 0.5s system)
END - ProcessID: 5796, peak process memory usage: 60748 kB, current process memory usage: 60644 kB
FME_END_PYTHON: evaluating python script from string...
FME_END_PYTHON: python script execution complete.
Translation was SUCCESSFUL

My value
THIS IS SHUTDOWN
My value

Basically environ is a global struct too.

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