columns()

Get structured metadata describing searchable CDA columns.

columns(*, return_data_as='', output_file='', sort_by='', debug=False, **filter_arguments)

Arguments

return_data_as

( string; optional: 'dataframe' or 'list' or 'tsv' ): Specify how columns() should return results: as a pandas DataFrame, a Python list, or as output written to a TSV file named by the user. If this argument is omitted, columns() will default to returning results as a DataFrame.

output_file

( string; optional ): If return_data_as='tsv' is specified, output_file should contain a resolvable path to a file into which columns() will write tab-delimited results.

sort_by

( string or list of strings; optional: any combination of 'table', 'column', 'data_type', and/or 'nullable'): Specify the column metadata field(s) on which to sort result data. Results will be sorted first by the first named field; groups of records sharing the same value in the first field will then be sub-sorted by the second field, and so on.

Any field with a suffix of ':desc' appended to it will be sorted in reverse order; adding ':asc' will ensure ascending sort order. Example: sort_by=[ 'table', 'nullable:desc', 'column:asc' ]

debug

( boolean; optional ): If set to True, print internal process details to the standard error stream.

Filter arguments

table

( string or list of strings; optional ): Restrict returned data to columns from tables whose names match any of the given strings. A wildcard (asterisk) at either end (or both ends) of each string will allow partial matches. Case will be ignored.

column

( string or list of strings; optional ): Restrict returned data to columns whose name matches any of the given strings. A wildcard (asterisk) at either end (or both ends) of each string will allow partial matches. Case will be ignored.

data_type

( string or list of strings; optional ): Restrict returned data to columns whose data type matches any of the given strings. A wildcard (asterisk) at either end (or both ends) of each string will allow partial matches. Case will be ignored.

nullable

( boolean; optional ): If set to True, restrict returned data to columns whose values are allowed to be empty; if False, return data only for columns requiring nonempty values.

description

( string or list of strings; optional ): Restrict returned data to columns whose description field matches any of the given strings. Wildcards will be automatically applied (end-to-end matching makes no sense here), emphasized by the name 'description_contains' and not 'description'. Case will be ignored.

exclude_table

( string or list of strings; optional ): Restrict returned data to columns from tables whose names do not match any of the given strings. A wildcard (asterisk) at either end (or both ends) of each string will allow partial matches. Case will be ignored.

Returns

pandas.DataFrame where each row is a metadata record describing one searchable CDA column comprising the following fields:

table (string: name of the CDA table containing this column) column (string: name of this column) data_type (string: data type of this column) nullable (boolean: if True, this column can contain null values) description (string: prose description of this column)

OR

list of column names

OR

returns nothing, but writes results to a user-specified TSV file