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Nappai Documentation

Slice Data

The Slice Data component lets you take a portion of a list of data items.
You give it a list, choose where to start and where to stop, and it returns only the items in that range. It’s useful when you only need a subset of a larger dataset for further processing.

How it Works

Internally, the component simply uses Python’s list slicing.
When you provide a list of Data objects, a start index, and an end index, it returns data_list[start_index:end_index].
If the indices are out of range, Python automatically adjusts them, so you won’t get an error—just an empty list or the available items.

Inputs

  • Data List: A list of Data objects that you want to slice.
  • Start Index: The position in the list where the slice should begin (inclusive). The default is 0.
  • End Index: The position in the list where the slice should end (exclusive). The default is 1.

Outputs

  • Sliced Data: The resulting list of Data objects that fall between the start and end indices. This output can be fed into other components that expect a list of data items.

Usage Example

Suppose you have a component that pulls 10 records from a database and you only want the first 5 to send to a report generator:

  1. Add Slice Data after the database pull component.
  2. Connect the database output to Data List.
  3. Set Start Index to 0 and End Index to 5.
  4. Connect Sliced Data to the report generator component.

The report generator will now receive only the first five records.

  • Join Data – Combine two lists of Data objects.
  • Filter Data – Keep only items that meet certain conditions.
  • Sort Data – Order a list of Data objects by a chosen field.

Tips and Best Practices

  • Check Index Bounds: If you’re unsure of the list length, use a larger end index; Python will safely return up to the list’s end.
  • Use Negative Indices: A negative start or end index counts from the end of the list, which can be handy for “last N items.”
  • Keep It Simple: For very large lists, consider filtering or joining before slicing to reduce memory usage.

Security Considerations

The component only manipulates data already present in the workflow; it does not access external services or the internet. Ensure that any Data objects you pass in are from trusted sources to avoid unintended data exposure.