Python 3.4 CSV 使用 in 函数删除项目

Question

这是我当前的代码，我当前的问题是搜索不返回任何内容。如何获得此变量的字符串值。

count = 0
with open("userDatabase.csv","r") as myFile:
    with open("newFile.csv","w") as newFile:
        row_count = sum(1 for row in myFile)
        print("aba")
        for x in range(row_count):
            print("aaa")
            for row in myFile:
                search = row[count].readline
                print(search)
                if self.delName.get("1.0","end-1c") in search:
                    count = count + 1
                else:
                    newFile.write(row[count])
                    count = count + 1

输出为:

aba
aaa
aaa

所以它运行了两次，这很好，因为我的 userDatabase 由两行数据组成。

相关文件包含以下数据:

"lukefinney","0000000","0000000","a"
"nictaylor","0000000","0000000","a"

Answer 1

您不能多次迭代打开的文件而不将文件对象倒回到开头。

您需要添加一个 file.seek(0) 调用，以便每次您想要再次从第一行开始读取时将文件读取器返回到开头:

myFile.seek(0)
for row in myFile:

你的代码的其余部分没有什么意义；迭代文件时，您会从文件中获取单独的行，因此每个 row 都是一个字符串对象。对字符串进行索引会为您提供仅包含一个字符的新字符串；例如，'foo'[1] 是字符 'o'。

如果您想跨与字符串不匹配的行进行复制，则根本不需要预先知道行数。您在这里不处理行列表，您可以单独查看每一行:

filter_string = self.delName.get("1.0","end-1c")

with open("userDatabase.csv","r") as myFile:
    with open("newFile.csv","w") as newFile:
        for row in myFile:
            if filter_string not in row:
                newFile.write(row)

这会进行子字符串匹配。如果需要匹配整列，请使用 csv module为您提供要匹配的各个列。该模块处理列值周围的引号:

import csv

filter_string = self.delName.get("1.0","end-1c")

with open("userDatabase.csv", "r", newline='') as myFile:
    with open("newFile.csv", "w", newline='') as newFile:
        writer = csv.writer(newFile)
        for row in csv.reader(myFile):
            # row is now a list of strings, like ['lukefinney', '0000000', '0000000', 'a']

            if filter_string != row[0]:  # test against the first column
                # copied across if the first column does not match exactly.
                writer.writerow(row)