通過更改Python中的字段來復制行

Question

我有一個很大的csv文件，其中包含兩列，例如： Id 和Vehicle

我喜歡復制行，如果車輛是“卡車”，而是放“汽車”。 我有此代碼，但有一個錯誤

這說

_csv.Error: iterator should return strings, not bytes (did you open the file in text mode?)

這是什么意思？ 我哪里錯了？

infilename = r'external carriers.csv'
outfilename = r'outputCSV.csv'

with open(infilename, 'rb') as fp_in, open(outfilename, 'wb') as fp_out:
    reader = csv.reader(fp_in, delimiter=",")
    writer = csv.writer(fp_out, delimiter=",")
    for row in reader:
        if len(row) == 2:
            if row == "truck":
                writer.writerow = "car"  

Answer 1

顯然，您已經以文本模式打開了需要rt的文件：

with open(infilename, 'rt') as fp_in, open(outfilename, 'wt') as fp_out:

另外，如果要檢查車輛類型，則需要檢查保留車輛名稱的row[1] ，然后重新分配該行並將該行寫入輸出文件。還要注意，您無需檢查長度如果您的性能為O（n）且對於大文件（特別是大行）的性能非常低效，則調用len函數可能會導致行嚴重惡化。

infilename = r'external carriers.csv'
outfilename = r'outputCSV.csv'

with open(infilename, 'rt') as fp_in, open(outfilename, 'wt') as fp_out:
    reader = csv.reader(fp_in, delimiter=",")
    writer = csv.writer(fp_out, delimiter=",")
    for row1,row2 in reader:
         if row2 == "truck":
            writer.writerow([row1,'car'])