How to convert a list of dictionaries to CSV format in Python, assuming the dictionaries can have different keys?

I have a list of dictionaries like that :

[
{'item1':'bla', 'item2':'bli', 'item3':'blu'},
{'item1'开发者_开发技巧:'love', 'item3':'python'}
]

Notice that dict 2 doesn't have key 'item2'. I want to produce a csv output as such, so I can insert everything into a SQL table:

item1,item2,item3
bla,bli,blu
love,,python

I found an easy way to do that if all dictionaries share the same keys, but I don't see how to do that elegantly if that is not the case.

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Use csv.DictWriter with the fieldnames and restval arguments.

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Something like

#Create a master list of keys
allKeys = ()
for row in YourListHere:
    allKeys.union(row.keys())

#Sort the keys
allKeys = list(allKeys).sorted()

#Go through printing the rows
for row in YourListHere:
    values = []
    for key in allKeys:
        #Add the values if it exists, if no key in this row add a blank
        if key in row:
            values.append(row[key])
        else:
            values.append('')
    print ','.join(values)