使用python运行bash命令并获取输出答案

【问题标题】：Using python to run bash commands and get Output使用python运行bash命令并获取输出
【发布时间】：2015-06-19 01:36:45
【问题描述】：

我想通过 Youtube-he 下载视频。所以，我写了程序，但它不工作。代码是

import os
l=["sets","relation_and_functions","Trig","Complex_Quad","Linear_inequalities","Permutation","Binomial","Sequence","Straight","conic","Three_d","Limit_Derivative","Stats","Probability","Math_reasoning"]
r=["https://www.youtube.com/playlist?list=PLD5EF274490578CC4","https://www.youtube.com/playlist?list=PL548FAD237A4B6D2E","https://www.youtube.com/playlist?list=PL42123C3873AED16F","https://www.youtube.com/playlist?list=PL880E3116D67E42FD","https://www.youtube.com/playlist?list=PLC5D1199BAE318878","https://www.youtube.com/playlist?list=PL812413BD6B55AA6E","https://www.youtube.com/playlist?list=PL78FAFAFA8496BCE1","https://www.youtube.com/playlist?list=PL6F57725E2DA8B557","https://www.youtube.com/playlist?list=PLA243228EA688A835","https://www.youtube.com/playlist?list=PL41B47FB4E23B392A","https://www.youtube.com/playlist?list=PLa2X112u1cdjdl-dsLJC1HaCeGrOarZZz","https://www.youtube.com/playlist?list=PLF6640F0A9F39F7BA","https://www.youtube.com/playlist?list=PL6FDE1AB3AE32E614","https://www.youtube.com/playlist?list=PL7FF5AD1CFF0981E5","https://www.youtube.com/playlist?list=PL13B63CD6FFAB9EA8"]
for i in range(len(l)):
    a=l[i]
    b=r[i]
    os.system("mkdir a")
    os.chdir("a")
    os.system("youtube-dl b")

【问题讨论】：

这些命令中的 a 和 b 是字符串文字，而不是您的变量。这也会创建嵌套目录（因为你永远不会 cd back up)... that is if it worked but each os.system` 是一个单独的 shell，所以 cd 实际上不会影响任何东西。
抱歉错误并感谢您的纠正。我在下面发布了一个可以正常工作的新代码

标签： python linux bash youtube download

【解决方案1】：

您需要传递实际变量，而不是字符串。您还应该特别使用子进程模块check_call：

l =["sets","relation_and_functions","Trig","Complex_Quad","Linear_inequalities","Permutation","Binomial","Sequence","Straight","conic","Three_d","Limit_Derivative","Stats","Probability","Math_reasoning"]
r=["https://www.youtube.com/playlist?list=PLD5EF274490578CC4","https://www.youtube.com/playlist?list=PL548FAD237A4B6D2E","https://www.youtube.com/playlist?list=PL42123C3873AED16F","https://www.youtube.com/playlist?list=PL880E3116D67E42FD","https://www.youtube.com/playlist?list=PLC5D1199BAE318878","https://www.youtube.com/playlist?list=PL812413BD6B55AA6E","https://www.youtube.com/playlist?list=PL78FAFAFA8496BCE1","https://www.youtube.com/playlist?list=PL6F57725E2DA8B557","https://www.youtube.com/playlist?list=PLA243228EA688A835","https://www.youtube.com/playlist?list=PL41B47FB4E23B392A","https://www.youtube.com/playlist?list=PLa2X112u1cdjdl-dsLJC1HaCeGrOarZZz","https://www.youtube.com/playlist?list=PLF6640F0A9F39F7BA","https://www.youtube.com/playlist?list=PL6FDE1AB3AE32E614","https://www.youtube.com/playlist?list=PL7FF5AD1CFF0981E5","https://www.youtube.com/playlist?list=PL13B63CD6FFAB9EA8"]

from subprocess import check_call

for direc, url in zip(l, r):
     check_call(["mkdir", direc])
     check_call(["youtube-dl", ele2],cwd=direc)

zip(l, r) 压缩每个列表中的相应元素，因此我们只需解压缩循环中的对。 cwd=direc 将设置下载文件的目录。

【讨论】：

对mkdir 的调用实际上应该是对os.mkdir() 的调用。不要为您自己可以轻松完成的事情调用外部流程。
效率，主要是。这将产生一个新进程，os.mkdir() 不会。
我刚刚用timeit 进行了测试，得到了 10776% 的差异（20.74 秒对 0.19 秒执行 10000 次）。如果你只做一次，这不会引起注意，但这是一个真的养成的坏习惯。
谢谢@Mike 我会改的

【解决方案2】：

不要使用os.system("mkdir a")，而是使用os.system("mdkir %s" % a)，否则会创建一个名为a的目录。不评估字符串中的变量名。出于同样的原因，请使用os.system("youtube-dl %s" % b)。此外，使用os.system("cd a") 切换到创建的目录，之后不要忘记使用os.system("cd ..") 切换回来。

【讨论】：

【解决方案3】：

import os
l=["sets","relation_and_functions","Trig","Complex_Quad","Linear_inequalities","Permutation","Binomial","Sequence","Straight","conic","Three_d","Limit_Derivative","Stats","Probability","Math_reasoning"]
r=["https://www.youtube.com/playlist?list=PLD5EF274490578CC4","https://www.youtube.com/playlist?list=PL548FAD237A4B6D2E","https://www.youtube.com/playlist?list=PL42123C3873AED16F","https://www.youtube.com/playlist?list=PL880E3116D67E42FD","https://www.youtube.com/playlist?list=PLC5D1199BAE318878","https://www.youtube.com/playlist?list=PL812413BD6B55AA6E","https://www.youtube.com/playlist?list=PL78FAFAFA8496BCE1","https://www.youtube.com/playlist?list=PL6F57725E2DA8B557","https://www.youtube.com/playlist?list=PLA243228EA688A835","https://www.youtube.com/playlist?list=PL41B47FB4E23B392A","https://www.youtube.com/playlist?list=PLa2X112u1cdjdl-dsLJC1HaCeGrOarZZz","https://www.youtube.com/playlist?list=PLF6640F0A9F39F7BA","https://www.youtube.com/playlist?list=PL6FDE1AB3AE32E614","https://www.youtube.com/playlist?list=PL7FF5AD1CFF0981E5","https://www.youtube.com/playlist?list=PL13B63CD6FFAB9EA8"]
c=[]
for i in l:
    c.append(i)
print c
for i in range(len(l)):
    q="mkdir "+l[i]
    l[i]=q
for j in range(len(r)):
    z="youtube-dl "+r[j]
    r[j]=z
print c
for i in range(len(l)):
    a=l[i]
    e=c[i]
    b=r[i]
    os.system(a)
    os.chdir(e)
    os.system(b)
    os.chdir("..")

这似乎可以正常工作。谢谢你。各位大侠帮忙

【讨论】：