python - python 脚本中的子进程错误

Question

我正在创建一个程序，我将在其中使用子进程转换文件。我用于转换的代码是:

import tornado.ioloop
import tornado.web
import os

print "If at any point you wish to quit the program hit Ctrl + C"

filetype = raw_input("What kind of file would you like to convert? Audio, Image, Video or Document: ")

if filetype == "Document":
    path = raw_input("Please drag and drop the directory in which the file is stored into the terminal:")
    os.chdir(path[1:-2])
    filename = raw_input("Please enter the name of the file you would like to convert, including the file-type. e.g. test.txt, however please do make sure that the file-name does not have any spaces:")
    Fileextension = raw_input("What filetype would you like the program to convert your file to. E.g. .txt: ")
    from subprocess import check_call   
    check_call(["unoconv " ,"-f ", Fileextension , + filename])

elif filetype == "Audio":
    path = raw_input("Please drag and drop the directory in which the file is stored into the terminal:")
    os.chdir(path[1:-2])
    filename = raw_input("Please enter the name of the file you would like to convert, including the file-type. e.g. test.txt, however please do make sure that the file-name does not have any spaces:")
    Fileextension = raw_input("What filetype would you like the program to convert your file to. E.g. .mp3: ")
    body, ext = os.path.splitext("filename")
    check_call(["ffmpeg" ,"-i", filename , + body + Fileextension])

elif filetype == "Video":
    path = raw_input("Please drag and drop the directory in which the file is stored into the terminal:")
    os.chdir(path[1:-2])
    filename = raw_input("Please enter the name of the file you would like to convert, including the file-type. e.g. test.txt, however please do make sure that the file-name does not have any spaces:")
    Fileextension = raw_input("What filetype would you like the program to convert your file to. E.g. .mp4: ")
    body, ext = os.path.splitext("filename")
    from subprocess import check_call   
    check_call(["ffmpeg" ,"-i", filename , + body + Fileextension])

elif filetype == "Image":
    path = raw_input("Please drag and drop the directory in which the file is stored into the terminal:")
    os.chdir(path[1:-2])
    filename = raw_input("Please enter the name of the file you would like to convert, including the file-type. e.g. test.txt, however please do make sure that the file-name does not have any spaces:")
    Fileextension = raw_input("What filetype would you like the program to convert your file to. E.g. .Jpeg: ")
    body, ext = os.path.splitext("filename")
    from subprocess import check_call   
    check_call(["ffmpeg" ,"-i", filename , + body + Fileextension])

当我现在运行程序时，出现错误:

  File "conversion.py", line 15, in <module>
    check_call(["unoconv " ,"-f ", Fileextension , + filename])
TypeError: bad operand type for unary +: 'str'

关于如何解决这个问题的任何想法。代码将不胜感激，但此时任何帮助将不胜感激。

Answer 1

正如错误所示，数组中同时包含 、 和 +。根据您正在做的其他事情，您可能希望删除 Fileextension 之后的 ,。您可能想将所有这些行更改为类似

subprocess.check_call(['unoconv', '-f', Fileextension, filename])

请注意，我还删除了“unoconv”中的空格，因为否则它会查找该空格作为可执行文件名称的一部分。

将列表传递给 check_call 时，每个列表元素都被视为进程的参数(这是第一个列表元素)。因此，如果您想运行 unoconv -f file.ext，您的 check_call 列表将变成一个 3 元素列表:['unoconv', '-f', ' .txt', '文件.ext']

您似乎混淆了字符串连接以将扩展名放在文件名上并构建参数列表。