将文件中的 CSV 数据读入内存的函数

Question

我正在尝试创建一个以列表形式将 csv 文件读入内存的函数。当我运行我的代码时，它给了我这个错误消息（“字符串索引必须是整数”）。我是不是弄错了。 下面是代码。感谢您的帮助

# create the empty set to carry the values of the columns

Hydropower_heading = []
Solar_heading = []
Wind_heading = []
Other_heading = []

def my_task1_file(filename):                              # defines the function "my_task1_file"
    with open(filename,'r') as myNew_file:                # opens and read the file
        for my_file in myNew_file.readlines():            # loops through the file

# read the values into the empty set created
            Hydropower_heading.append(my_file['Hydropower'])
            Solar_heading.append(my_file['Solar'])
            Wind_heading.append(my_file['Wind'])
            Other_heading.append(my_file['Other'])

#Hydropower_heading = int(Hydropower)
#Solar_heading = int(Solar)
#Wind_heading = int(Wind)
#Other_heading = int(Other)            
            
my_task1_file('task1.csv')                                # calls the csv file into the function 

# print the Heading and the column values in a row form
print('Hydropower: ', Hydropower_heading)
print('Solar: ', Solar_heading)
print('Wind: ', Wind_heading)
print('Other: ', Other_heading)

Answer 1

我们可以使用csv.DictReader method按列读取CSV文件。

代码：(code.py)

import csv


def my_task1_file(filename):  # defines the function "my_task1_file"
    Hydropower_heading = []
    Solar_heading = []
    Wind_heading = []
    Other_heading = []
    with open(filename, newline='\n') as csvfile:
        reader = csv.DictReader(csvfile)
        for row in reader:
            # read the values into the empty set created
            Hydropower_heading.append(row['Hydropower'])
            Solar_heading.append(row['Solar'])
            Wind_heading.append(row['Wind'])
            Other_heading.append(row['Other'])
    return Hydropower_heading, Solar_heading, Wind_heading, Other_heading

if __name__ == "__main__":
    Hydropower_heading, Solar_heading, Wind_heading, Other_heading = my_task1_file('task1.csv')

    # print the Heading and the column values in a row form
    print('Hydropower: ', Hydropower_heading)
    print('Solar: ', Solar_heading)
    print('Wind: ', Wind_heading)
    print('Other: ', Other_heading)

task1.csv:

Hydropower,Solar,Wind,Other
5,6,3,8
6,8,5,12
3,6,9,7

输出：

Hydropower:  ['5', '6', '3']
Solar:  ['6', '8', '6']
Wind:  ['3', '5', '9']
Other:  ['8', '12', '7']

说明：

• __main__ 条件将检查文件是否直接运行。如果使用python code.py 直接运行文件，它将执行该部分。否则如果我们从另一个python文件中导入code.py，这部分将不会被执行。
• 您可以根据需要删除__main__ 块，如下所示。但是，在使用__main__ 块从另一个python 文件导入一个python 文件时，将方法与执行分开是一个很好的做法。让我知道它是否能消除您的困惑。

code.py（没有__main__）：

import csv


def my_task1_file(filename):  # defines the function "my_task1_file"
    Hydropower_heading = []
    Solar_heading = []
    Wind_heading = []
    Other_heading = []
    with open(filename, newline='\n') as csvfile:
        reader = csv.DictReader(csvfile)
        for row in reader:
            # read the values into the empty set created
            Hydropower_heading.append(row['Hydropower'])
            Solar_heading.append(row['Solar'])
            Wind_heading.append(row['Wind'])
            Other_heading.append(row['Other'])
    return Hydropower_heading, Solar_heading, Wind_heading, Other_heading

Hydropower_heading, Solar_heading, Wind_heading, Other_heading = my_task1_file('task1.csv')

print('Hydropower: ', Hydropower_heading)
print('Solar: ', Solar_heading)
print('Wind: ', Wind_heading)
print('Other: ', Other_heading)

参考资料：

• csv.DictReader method
• __main__ documentation from Python website

Answer 2

由于错误是“字符串索引必须是整数”，因此您必须使用不能将字符串值作为索引的数据类型。在这段代码中...

for my_file in myNew_file.readlines():
     
     Hydropower_heading.append(my_file['Hydropower'])
     Solar_heading.append(my_file['Solar'])
     Wind_heading.append(my_file['Wind'])
     Other_heading.append(my_file['Other'])

...您正在使用“Hydropower”、“Solar”、“Wind”和“Other”作为索引值，它们不能是 my_file 的有效索引值，我假设它是字符串数据类型，因为您正在读取文件myNew_file。如果您将这些值更改为适当的整数，则该错误将不再出现。