Python追加列标题并将列值从列表追加到csv

Question

我正在尝试附加列标题（硬编码）并将列值从列表附加到现有的 csv。我没有得到想要的结果。

方法 1 是在现有 csv 文件上附加结果。方法 2 将现有 csv 的副本克隆到 temp.csv 中。这两种方法都没有得到我想要的输出。在结果 1 中，它只是附加在最后一行单元格之后。在结果 2 中，所有列表值都附加在每一行上。预期的结果是我正在寻找的。

我在下面包含了我的代码。感谢任何输入或指导。

现有的 CSV Test.csv

Type,Id,TypeId,CalcValues
B,111K,111Kequity(long) 111K,116.211768
C,111N,B(long) 111N,0.106559957
B,111J,c(long) 111J,20.061634

代码 - 方法 1 和 2

final_results = ['0.1065599566767107', '0.0038113334533441123', '20.061623176440904']

# Method1
csvfile = "test.csv"
with open(csvfile, "a") as output:
    writer = csv.writer(output, lineterminator='\n')
    for val in final_results:
        writer.writerow([val])  

# Method2
with open("test.csv", 'rb') as input, open('temp.csv', 'wb') as output:
    reader = csv.reader(input, delimiter = ',')
    writer = csv.writer(output, delimiter = ',')

    all = []
    row = next(reader)
    row.insert(5, 'Results')
    all.append(row)

    for row in reader:
        for i in final_results:
            print type(i)
            row.insert(5, i)
        all.append(row)
    writer.writerows(all)

方法 1 的结果

Type,Id,TypeId,CalcValues
B,111K,111Kequity(long) 111K,116.211768
C,111N,B(long) 111N,0.106559957
B,111J,c(long) 111J,20.0616340.1065599566767107
0.0038113334533441123
20.061623176440904

方法 2 的结果

Type,Id,TypeId,CalcValues,Results
B,111K,111Kequity(long) 111K,116.211768,0.1065599566767107,20.061623176440904,0.0038113334533441123
C,111N,B(long) 111N,0.106559957,0.1065599566767107,20.061623176440904,0.0038113334533441123
B,111J,c(long) 111J,20.061634,0.1065599566767107,20.061623176440904,0.0038113334533441123

预期结果

Type,Id,TypeId,CalcValues,ID
B,111K,111Kequity(long) 111K,116.211768,0.1065599566767107
C,111N,B(long) 111N,0.106559957,20.061623176440904
B,111J,c(long) 111J,20.061634,0.0038113334533441123

Answer 1

第一种方法肯定会失败：您不想添加新行而是添加新列。回到第二种方法：

您可以插入标题，但随后您将遍历每一行的结果，而您需要对其进行迭代。

为此，我从final_results 列表（使用__iter__()）创建一个迭代器，然后我调用it.next 并附加到每一行（无需在最后插入，只需附加）

我删除了 all 大列表，因为 1) 你可以一次写一行，节省内存，以及 2) all 是一个预定义的函数。避免将其用作变量。

final_results = ['0.1065599566767107', '0.0038113334533441123', '20.061623176440904']

# Method2
with open("test.csv", 'rb') as input, open('temp.csv', 'wb') as output:
    reader = csv.reader(input, delimiter = ',')
    writer = csv.writer(output, delimiter = ',')


    row = next(reader)  # read title line
    row.append("Results")
    writer.writerow(row)  # write enhanced title line

    it = final_results.__iter__()  # create an iterator on the result

    for row in reader:
        if row:  # avoid empty lines that usually lurk undetected at the end of the files
            try:
                row.append(next(it))  # add a result to current row
            except StopIteration:
                row.append("N/A")     # not enough results: pad with N/A
            writer.writerow(row)

结果：

Type,Id,TypeId,CalcValues,Results
B,111K,111Kequity(long) 111K,116.211768,0.1065599566767107
C,111N,B(long) 111N,0.106559957,0.0038113334533441123
B,111J,c(long) 111J,20.061634,20.061623176440904

注意：如果我们将"Results" 包含在final_results 变量中，我们甚至不需要以不同的方式处理第一行。

注意2：值似乎错误：final_results 似乎与预期输出的顺序不同。而Result 列已变为ID，但这很容易纠正。

Answer 2

import csv

HEADER = "Type,Id,TypeId,CalcValues,ID"
final_results = ['0.1065599566767107', '20.061623176440904', '0.0038113334533441123']

with open("test.csv") as inputs, open("tmp.csv", "wb") as outputs:
    reader = csv.reader(inputs, delimiter=",")
    writer = csv.writer(outputs, delimiter=",")

    reader.next()  # ignore header line
    writer.writerow(HEADER.split(","))  

    for row in reader:
        writer.writerow(row + [final_results.pop(0)])

我将header字段存入HEADER并切换final_results的第2个和第3个元素，使用pop(0)移除并返回final_results的第一个元素

输出：

Type,Id,TypeId,CalcValues,ID
B,111K,111Kequity(long) 111K,116.211768,0.1065599566767107
C,111N,B(long) 111N,0.106559957,20.061623176440904
B,111J,c(long) 111J,20.061634,0.0038113334533441123