CODEWITHSUNDEEP
pythoncsv
Koppis
Koppis

Reputation: 109

Python analyzing and changing data values

I have tried to make my program work, but as I don't have a lot of experience, I have faced a lot of problems. The idea of my work is that I analyze the data of the csv file and change the negative values to 0. So far I have managed to get all the data from the file and save it to a list, and manually assigning the "start" and "end" times of the file. 

import csv

data = []

filename = str(input("Give the file name: "))
    with open(filename) as csvfile:
        spamreader = csv.reader(csvfile, delimiter=';')
        for row in spamreader:
            data.append(row)

    print("File", filename, "is opened,", len(data),"rows will be analyzed.")

    data.pop(0) #deletes the header   

    print (f'Analyzing data between dates {data[0][0]} and {data[1097][0]}.') #data[row][column]

How is it possible to change the negative values in the data (screenshot) to 0, and then save everything to a new csv file? Help would be massivly appreciated. screenshot inside the CSV file asd

[In the actual data file there is 1000+ rows]

Upvotes: 1

Views: 347

Answers (2)

BernardL
BernardL

Reputation: 5434

If your file contains only numbers you can try the code below:

import csv
from collections import defaultdict

def convert(item):
    try:
        item = float(item)
        if item < 0:
            return 0
        else:
            return item
    except ValueError:
        return item

sums = defaultdict(list)

with open('Data.csv', 'r') as inp, open('output.csv', 'w', newline = '') as outp:
    reader = csv.reader(inp, delimiter = ';')
    writer = csv.writer(outp, delimiter = ';', dialect = 'excel')
    headers = next(reader)
    for line in reader:
        line = [convert(i) for i in line]
        sums[line[0]].append(line[1])
        writer.writerow(line)

for k,v in sums.items():
    print('key: {} total: {}'.format(k,sum(v)))

Firstly you can use the with context manager to open both files that you are going to read and write, from and to respectively. Then instead of storing it into a list, you can transform your data and directly write it to your target file, here named output.csv. The for line in reader here loops through the lines and transforms each value into an absolute integer before writing it to the file.

I added the defaultdict from the Python standard library if you want to store the values into a dictionary to use them. The dictionary sums will include a key by date and its values. To print the sum by days, you can simply use a string format to print the key and the summed values.

Upvotes: 1

moo
moo

Reputation: 2175

This is very easily achieved using a pandas DataFrame:

import pandas as pd

c = pd.read_csv('inputcsvfile.csv')
processed_csv = c[c > 0].fillna(value=0)
processed_csv.to_csv('outputcsvfile.csv')

Pandas is an external library so you would need to install it (pip install pandas) before you can use this solution

Upvotes: 0

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