Foundations-03.py

## verbose version
delayed_read_csv = delayed(pd.read_csv)
a = delayed_read_csv(filenames[0])
b = delayed_read_csv(filenames[1])
c = delayed_read_csv(filenames[2])

delayed_len = delayed(len)
na = delayed_len(a)
nb = delayed_len(b)
nc = delayed_len(c)

delayed_sum = delayed(sum)

total = delayed_sum([na, nb, nc])
%time print(total.compute())


## concise version
csvs = [delayed(pd.read_csv)(fn) for fn in filenames]
lens = [delayed(len)(csv) for csv in csvs]
total = delayed(sum)(lens)
%time print(total.compute())