Python：有没有办法在调用writerow（）之前更新DictWriter的键（列）？

Question

csv.Dictwriter is instantiated thus:

 class csv.DictWriter(csvfile, fieldnames, restval='', extrasaction='raise', dialect='excel', *args, **kwds)

fieldsnames is a sequence of keys, or in my case, a dict.

Here's my question; after instantiating DictWriter with a certain dict, I wish to remove some of the keys (and by extension, values) of fieldnames before calling writerow() . For reasons I won't get into, I can only tell the code which keys to remove after DictWriter has been instantiated. Dict has just 3 methods:

writerheader
writerow
writerows

.. none of which are any help. Based on my testing, it seems that when DictWriter is instantiated, it sets the column names of the csv-to-be according to fieldnames . And any change made to fieldnames after instantiation has no effect on the column headers that will be generated. Because DictWriter defines the columns at instantiation, am I stuck with these? Or is there a way around this?

Answer 1

Suppose you have a dict like -

d = {'a': 1, 'b': 2, 'c': 3, 'd': 4}

then you can use csv.writer as follows:

f = open('abc.csv', 'wb')
csv_writer = csv.writer(f, dialect=csv.excel, delimiter=',', quotechar='"', quoting=csv.QUOTE_ALL)

for row in rows:
    csv_writer.writerow([row['b'], row['c'])  # Assuming we dont want keys 'a' and 'b' to be written
f.close()