python - 类型错误 : unsupported operand type(s) for -: 'str' and 'int' Python

Question

我对编程很陌生，Python 是我的第一种编程语言，所以请友善。我运行了以下代码:

searchmovie = raw_input("What movie would you like to rent?\n").lower()
searchindex = dvds.index(searchmovie)
r = csv.reader(open('dvd_info.csv'))
lines = [l for l in r]
currentvalue = lines[searchindex][2]
lines[searchindex][2] = currentvalue - 1
writer = csv.writer(open('tmp.csv', 'w'))
writer.writerows(lines)

我得到了错误:

    lines[searchindex][2] = currentvalue - 1
TypeError: unsupported operand type(s) for -: 'str' and 'int'

我做错了什么？

Answer 1

您的currentvalue是一个字符串，您需要先将其转换为int:

lines[searchindex][2] = str(int(currentvalue) - 1)

此代码摘自@ozgur 的评论。