How can I write a list of tuples to a csv file where the first element of the tuple is a dictionary?

Question

I have a list of tuples in the form:

data = [({1: 0.1723, 2: 0.890, 3: 1.0}, 'a'),
        ({1: 0.0, 2: 1.0, 3: 0.667}, 'b'),
        ({1: 0.223, 2: 0.336, 3: 1.0}, 'b')]

The second element of each tuple is simply a string.

How can I write it to a csv file so that the contiguous columns correspond to each element?

ie: for data[1] : col1 = 0.1723 , col2 = 0.890 , col3 = 1.0 , col4 = 'a' ?

Answer 1

You could use a generator expression to generate all rows at once, which come in 2 parts.

• sorted list of values of your dictionaries according to keys
• single-element list of the string

this code:

import csv

data = [({1: 0.1723, 2: 0.890, 3: 1.0}, 'a'),
        ({1: 0.0, 2: 1.0, 3: 0.667}, 'b'),
        ({1: 0.223, 2: 0.336, 3: 1.0}, 'b')]

with open("output.csv","w",newline="") as f:  # python 2: just: ,"wb")
    cw = csv.writer(f)
    cw.writerows([v for _,v in sorted(d.items())] + [s] for d,s in data)

creates the following file:

0.1723,0.89,1.0,a
0.0,1.0,0.667,b
0.223,0.336,1.0,b

for d,s in data is just a nice way to unpack the dictionary (first item) and the value (second item). And the csv module converts floats & integers to string, no need to bother for that.

Answer 2

you can do this as follows:

import csv

data = [({1: 0.1723, 2: 0.890, 3: 1.0}, 'a'), ({1: 0.0, 2: 1.0, 3: 0.667}, 'b'), ({1: 0.223, 2: 0.336, 3: 1.0}, 'b')]
rows = []
for the_dict, the_char in data:
    row = []
    # get values from dictionary and add it to row
    for x in the_dict.values():
        row.append(x)
    # add char
    row.append(the_char)
    # ad row to rows list
    rows.append(row)

with open("output.csv", "wb") as f:
    writer = csv.writer(f)
    writer.writerows(rows)

Answer 3

Here is another solution:

import csv

data = [({1: 0.1723, 2: 0.890, 3: 1.0}, 'a'),
        ({1: 0.0, 2: 1.0, 3: 0.667}, 'b'),
        ({1: 0.223, 2: 0.336, 3: 1.0}, 'b')]

def make_row(elements):
    row = list()
    for obj in elements:
        if isinstance(obj, dict):
            row += obj.values()
        else:
            row.append(obj)
    return row

with open('output.csv', 'w') as handle:
    writer = csv.writer(handle)
        for row in data:
            writer.writerow(make_row(row))