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Column.auto_cast

auto_castshrink_types

Group: Conversions
Aliases: auto_value_type

Documentation​

Change the value type of the column to a more specific one, based on its contents.

Arguments​

  • shrink_types: If set True, smaller types will be chosen if possible, according to the rules below. Defaults to False.

Remarks​

Auto Type Selection Rules​

  • If a Mixed column can be assigned a single type, like Char or Integer, that will be used.
  • Text columns are not parsed. To do that, use the parse method.
  • If a Float column contains only integers, it will be converted to an Integer column.
  • If a Decimal column contains only integers that could fit in a 64-bit integer storage, it will be converted to an Integer column.
  • If shrink_types is False (default), no other transformations are applied.
  • However, if shrink_types is set to True, then:
    • Integer columns will be assigned the smallest size that can fit all values (down to 16-bit integers; converting to the Byte type has to be done manually through cast).
    • If all elements in a text column have the same length, the type will become fixed length.
    • Otherwise, if a text column is variable length, but all text elements are no longer than 255 characters, the column will get a max length of 255. Otherwise, the column size limit will stay unchanged.