CSV ElasticDictWriter

DictWriter, built on top of csv.DictWriter, that supports automatic extension of headers according to what data it receives. The result file always has a complete header (as defined by fieldnames) or it is extended if some new columns are introduced in the data. It always produces a valid CSV (missing columns are filled with blanks). It uses a series of cached writers / files that are merged into a single one with final set of columns on close()

Installation

The package may be installed via PIP:

pip install keboola.csvwriter

NOTE: If not using "with" statement, close() method must be called at the end of processing to get the result.

NOTE: Does not keep the order of rows added - the rows containing additional headers always come first:

Example:

from keboola.csvwriter import ElasticDictWriter
file = '/test/test.csv'
wr = ElasticDictWriter(file, ["a", "b" , "c"])
wr.writeheader()
wr.writerow({"a":1,"b":2})
wr.writerow({"b":2, "d":4})
wr.close()

leads to CSV with following content:

May be also used with with statement to automatically close once finished:

from keboola.csvwriter import ElasticDictWriter
file = '/test/test.csv'
with ElasticDictWriter(file, ["a", "b" , "c"]) as wr:
    wr.writeheader()
    wr.writerow({"a":1,"b":2})
    wr.writerow({"b":2, "d":4})

# get final headers
final_header = wr.fieldnames

NOTE: The final column list is stored in fieldnames property:

columns = writer.fieldnames