在python中排序时列出索引超出范围

Question

我正在尝试将 CSV 文件读入列表，然后根据列表的前两列对其进行排序（首先按第一列，如果第一列相同，则按第二列）。这就是我正在做的：

def sortcsvfiles(inputfilename,outputfilename):
    list1=[]
    row1=[]
    with open(inputfilename,'rt') as csvfile1:
        reader=csv.reader(csvfile1)
        cnt=0       
        for row in reader:
            if cnt==0:        #skip first row as it contains header information
                row1=row
                cnt+=1
                continue    
            list1.append((row)) 

        list1.sort(key=lambda ro: (int(ro[0]),int(ro[1])))

    list1.insert(0, row1)
    with open(outputfilename,'wt') as csvfile1:
        writer=csv.writer(csvfile1, lineterminator='\n')
        for row in list1:
            writer.writerow(row)

但我收到以下错误：

  File "C:\Users\50004182\Documents\temp.py", line 37, in <lambda>
    list1.sort(key=lambda ro: (int(ro[0]),int(ro[1])))
IndexError: list index out of range

我该如何解决这个问题？

Answer 1

您的文件中可能有一个空行。也许是最后一个。例如，您可以忽略空行：

def sortcsvfiles(inputfilename,outputfilename):
    with open(inputfilename,'rt') as csvfile:
        reader = csv.reader(csvfile)
        header = next(reader)
        data = [row for row in reader if row] # ignore empty lines
        data.sort(key=lambda ro: (int(ro[0]),int(ro[1])))

    with open(outputfilename,'wt') as csvfile:
        writer=csv.writer(csvfile, lineterminator='\n')
        writer.writerow(header)
        writer.writerows(data)

Answer 2

发生错误是因为您至少有一行没有 2 列。它可能有 1 甚至 0。

您可以在添加行之前对此进行测试：

if len(row) > 1:
    list1.append(row) 

要对所有行进行排序但跳过第一个标题，您可以使用next() 函数（请参阅a previous answer of mine）；也许使用sorted() 函数：

def sortcsvfiles(inputfilename, outputfilename):
    with open(inputfilename,'rt') as csvfile1:
        reader = csv.reader(csvfile1)
        headers = next(reader, None)  # get one row, or None if there are no rows
        rows = sorted(
            (r for r in reader if len(r) > 1),
            key=lambda r: (int(r[0]), int(r[1])))

    with open(outputfilename,'wt') as csvfile1:
        writer = csv.writer(csvfile1, lineterminator='\n')
        if headers:
            writer.writerow(headers)
        writer.writerows(rows)

我使用writer.writerows() 在一次调用中写入整个排序行列表。