CODEWITHSUNDEEP
pythonpandascsv
Joseph
Joseph

Reputation: 1

How to convert single strings to floats in csv_reader

I want to convert specific strings to floats with the csv read file, but cant figure it out.

with open('diamonds_testing.csv') as csv_file:
    csv_reader = csv.reader(csv_file)
    diamond = list(csv_reader)

print(diamond[1])
print(diamond[2])

output:

['0.23', 'Ideal', 'E', 'SI2', '55', '3.95', '3.98', '2.43']
         
['0.31', 'Very Good', 'J', 'SI1', '62', '4.39', '4.43', '2.62']

I want to output to be floats in columns 0,4,5,6,7. Thank you.

Upvotes: 0

Views: 56

Answers (3)

Ailurophile
Ailurophile

Reputation: 3005

you can try

def validate(num):
    try:
        return int(num)
    except (ValueError, TypeError):
        try:
            return float(num)
        except (ValueError, TypeError):
            return num

with open('diamonds_testing.csv') as csv_file:
    csv_reader = csv.reader(csv_file)
    diamond = list(csv_reader)

    for i in diamond:
        diamond[i] = [validate(v) for v in diamond[i]]

Sample output

print(diamond[1])
print(diamond[2])

Output:

[0.23, 'Ideal', 'E', 'SI2', 55, 3.95, 3.98, 2.43]
[0.31, 'Very Good', 'J', 'SI1', 62, 4.39, 4.43, 2.62]

Upvotes: 0

Serge Ballesta
Serge Ballesta

Reputation: 149185

The csv module is a lower level module (and far less resource consuming) that the huge pandas library. As a result, it never tries to interpret the data and only split rows into strings. If you know that some columns should contain integer or floating point values, you will have to convert the values yourself.

with open('diamonds_testing.csv') as csv_file:
    float_columns = (O, 4, 5, 6, 6)
    csv_reader = csv.reader(csv_file)
    diamond = [[float(v) if i in float_columns else v for i, v in enumerate(row)]
               for row in csv_reader]

Or you can have Pandas to guess the data types:

diamond = [row[1].to_list()
           for row in pd.read_csv('diamonds_testing.csv', header=None).iterrows()]

Upvotes: 0

Eden Berdugo
Eden Berdugo

Reputation: 339

    with open('diamonds_testing.csv') as csv_file:
    csv_reader = csv.reader(csv_file)
    diamond = list(csv_reader)
    lines = []
    for line in diamond:
        for i in [0, 4, 5, 6, 7]:
            line[i] = float(line[i])
        lines.append(line)
    print(lines)

float () to do cast. to pass line by line use

for line in diamond:

Upvotes: 1

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