cs.csvutils 20220606

CSV file related facilities

Utility functions for CSV files.

Latest release 20220606:

• Make csv_reader() a generator to cue the @strable decorator.
• Plumb the new optional snake_case parameter.

In python 2 the stdlib CSV reader reads 8 bit byte data and returns str objects; these need to be decoded into unicode objects. In python 3 the stdlib CSV reader reads an open text file and returns str objects (== unicode). So we provide csv_reader() generators to yield rows containing unicode.

Function csv_import(fp, class_name=None, column_names=None, computed=None, preprocess=None, mixin=None, snake_case=False, **kw)

Read CSV data where the first row contains column headers. Returns a row namedtuple factory and an iterable of instances.

Parameters:

• fp: a file object containing CSV data, or the name of such a file
• class_name: optional class name for the namedtuple subclass used for the row data.
• column_names: optional iterable of column headings; if provided then the file is not expected to have internal column headings
• computed: optional keyword parameter providing a mapping of str to functions of self; these strings are available via getitem
• preprocess: optional keyword parameter providing a callable to modify CSV rows before they are converted into the namedtuple. It receives a context object and the data row. It may return the row (possibly modified), or None to drop the row.
• mixin: an optional mixin class for the generated namedtuple subclass to provide extra methods or properties

All other keyword parameters are passed to csv_reader(). This is a very thin shim around cs.mappings.named_column_tuples.

Examples:

  >>> rowtype, rows = csv_import(['a, b', '1,2', '3,4'], class_name='Example_AB')
  >>> rowtype     #doctest: +ELLIPSIS
  <function named_row_tuple.<locals>.factory at ...>
  >>> list(rows)
  [Example_AB(a='1', b='2'), Example_AB(a='3', b='4')]

  >>> rowtype, rows = csv_import(['1,2', '3,4'], class_name='Example_DEFG', column_names=['D E', 'F G '])
  >>> list(rows)
  [Example_DEFG(d_e='1', f_g='2'), Example_DEFG(d_e='3', f_g='4')]

Function csv_reader(arg, *a, **kw)

Read the file fp using csv.reader. fp may also be a filename. Yield the rows.

Warning: ignores the encoding and errors parameters because fp should already be decoded.

Function csv_writerow(csvw, row, encoding='utf-8')

Write the supplied row as strings encoded with the supplied encoding, default 'utf-8'.

Function xl_import(workbook, sheet_name=None, skip_rows=0, **kw)

Read the named sheet_name from the Excel XLSX file named filename as for csv_import. Returns a row namedtuple factory and an iterable of instances.

Parameters:

• workbook: Excel work book from which to load the sheet; if this is a str then the work book is obtained from openpyxl.load_workbook()
• sheet_name: optional name of the work book sheet whose data should be imported; the default (None) selects the active worksheet

Other keyword parameters are as for cs.mappings.named_column_tuples.

NOTE: this function requires the openpyxl module to be available.

Release Log

Release 20220606:

• Make csv_reader() a generator to cue the @strable decorator.
• Plumb the new optional snake_case parameter.

Release 20201228: Python 3 csv_reader new a generator.

Release 20191118: xl_import: make sheet_name parameter optional with useful default

Release 20190103: Documentation updates.

Release 20180720: csv_import and xl_import function to load spreadsheet exports via cs.mappings.named_column_tuples.

Release 20170608: Recode using new simpler cs.sharedfile.SharedAppendLines.

Release 20160828:

• Update metadata with "install_requires" instead of "requires".
• Python 2 and 3 portability fixes.
• Assorted minor improvements.

Release 20150116: Initial PyPI release.