I append features from one class to other (using arcpy.Append_management including FieldMappings). The issue is I overshoot the length of target field. I do wonder why Append_management does not deal with such issue, anyway...

For now I can increase the length of target field which fixed the issue. But I still need somehow check the length of input string. And do sub-string if needed so the tool won't crash whenever there too long string in input data. Any simple way to achieve this?

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I decided to not use arcpy.Append_management as it crashes on input longer than length of target field. As far as I know there is no way to check. For this reason I would suggest NOT to use Append together with field_mapping unless you are completely sure the inputs can't hit the length limitation of output.

Not sure if Append checks input/output field length when not using field mapping. If it checks only field names and types there is again space for crash.

At the end I decided to use combination of arcpy.da.SearchCursor and arcpy.da.InsertCursor and before Insert use slicing with the target field length to make sure there is no overshoot.

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