Question

I have a nested list like this:

[['Bike No.', 'Purchase Date', 'Batt %', 'Last Maintenance', 'KM since Last', 'Service?'], 
['T101', '10/4/2016', '55', '10/1/2017', '25.08', 'N'], 
['T102', '1/7/2016', '10', '15/5/2017', '30.94', 'N'], 
['T103', '15/11/2016', '94', '13/6/2017', '83.16', 'Y'], 
['T104', '25/4/2017', '58', '10/1/2017', '25.08', 'N'], 
['T105', '24/5/2017', '5', '20/6/2017', '93.8', 'Y']]

I want to be able to create a csv file and put in each list into every line ,how do I do it ? In addition ,I want to be able to overwrite the data with a new one whenever ,the list is updated ,how can I do this? Thanks

As of now ,here is the code I have:

        with open(filepath + 'Bike_List_With_Service.csv','w',newline='') as file:
        a=csv.writer(file,delimiter=',')
        data=data
        a.writerows(data)#write each line of data

Answer 1

Use the csv module

import csv

rows = [['Bike No.', 'Purchase Date', 'Batt %', 'Last Maintenance', 'KM since Last', 'Service?'], 
['T101', '10/4/2016', '55', '10/1/2017', '25.08', 'N'], 
['T102', '1/7/2016', '10', '15/5/2017', '30.94', 'N'], 
['T103', '15/11/2016', '94', '13/6/2017', '83.16', 'Y'], 
['T104', '25/4/2017', '58', '10/1/2017', '25.08', 'N'], 
['T105', '24/5/2017', '5', '20/6/2017', '93.8', 'Y']]

with open('output.csv', 'w') as f:
    writer = csv.writer(f)
    writer.writerows(rows)

Output:

Bike No.,Purchase Date,Batt %,Last Maintenance,KM since Last,Service?
T101,10/4/2016,55,10/1/2017,25.08,N
T102,1/7/2016,10,15/5/2017,30.94,N
T103,15/11/2016,94,13/6/2017,83.16,Y
T104,25/4/2017,58,10/1/2017,25.08,N
T105,24/5/2017,5,20/6/2017,93.8,Y

Answer 2

为了能够更新现有值（假设基于自行车号码），您首先需要读取文件并将数据存储在字典中。然后，您可以根据新数据更新字典条目。现在，您可以对字典中的键进行排序（如果希望文件保持排序顺序），并将更新的数据写回文件。例如：

import csv

filename = 'Bike_List_With_Service.csv'
header = ['Bike No.', 'Purchase Date', 'Batt %', 'Last Maintenance', 'KM since Last', 'Service?']
existing_data = {}

new_data = [
    ['T101', '10/4/2016', '55', '10/1/2017', '25.08', 'N'], 
    ['T102', '1/7/2016', '10', '15/5/2017', '30.94', 'N'], 
    ['T103', '15/11/2016', '94', '13/6/2017', '83.16', 'Y'], 
    ['T104', '25/4/2017', '58', '10/1/2017', '25.08', 'N'], 
    ['T105', '24/5/2017', '5', '20/6/2017', '93.8', 'Y']]

# try and read in existing data from the file
try:
    with open(filename, 'r', newline='') as f_input:
        csv_input = csv.reader(f_input)
        next(csv_input) # skip over existing header

        for row in csv_input:
            existing_data[row[0]] = row[1:]
except FileNotFoundErrors as e:
    pass

# update the existing data with new_data
for row in new_data:
    existing_data[row[0]] = row[1:]

# write the updated data back to the csv file    
with open(filename, 'w', newline='') as f_output:
    csv_output = csv.writer(f_output)
    csv_output.writerow(header)

    for row in sorted(existing_data):
        csv_output.writerow([row] + existing_data[row])

这将首先尝试并读取现有文件（如果文件不存在，它将继续）。字典键保存自行车编号，其值包含剩余的行值。

通过使用Python的csv库，它负责读取一行逗号分隔值并将它们自动转换为每行列表。如果值中带有引号的字符串，它也会处理它。如果您不想使用图书馆，另一种方法是阅读该行的每一行，删除最后一行的新行，并使用split()创建您的列表。

Answer 3

import os
        if (not os.path.isfile("/{}/Bike_List_With_Service.csv".format(filepath))):#checks if Bike_List_With_Service.csv is in path
            with open(filepath + 'Bike_List_With_Service.csv','w',newline='') as file:#creates a new csv file named 'Bikelistwithservice.csv'
                a=csv.writer(file,delimiter=',')
                data=data
                a.writerows(data)#write each line of data
        else:
            file_to_be_overwrite="Bike_List_With_Service.csv"
            ov=open(filepath+file_to_be_overwrite,"w")
            ov.truncate()       #clears everything in the file and reenter the data
            ov.close()
            with open(filepath + 'Bike_List_With_Service.csv','w',newline='') as file:#creates a new csv file named 'Bikelistwithservice.csv'
                a=csv.writer(file,delimiter='')
                data=data
                a.writerows(data)#write each line of data

Create a csv file with python and put in nested list to it

3 个答案: