为什么os.system（）放置在for循环时运行？

Question

我有以下的（伪）代码：

import os 

for s in settings: 
    job_file = open("new_file_s.sh", "w") 
    job_file.write("stuff that depends on s") 
    os.system(command_that_runs_file_s) 

不幸的是，什么情况是，对应于s = settings[0]文件不被执行，但随后s = settings[1]执行。显然，os.system()不喜欢运行最近使用open()创建的文件，尤其是在for循环的相同迭代中。

对我的修复是确保通过os.system()执行任何文件中的for循环先前迭代初始化：

import os 

# Stagger so that writing happens before execution: 
job_file = open("new_file_settings[0].sh", "w") 
job_file.write("stuff that depends on settings[0]") 

for j in range(1, len(settings)): 
    job_file = open("new_file_settings[j].sh", "w") 
    job_file.write("stuff that depends on settings[j]") 

    # Apparently, running a file in the same iteration of a for loop is taboo, so here we make sure that the file being run was created in a previous iteration: 
    os.system(command_that_runs_file_settings[j-1]) 

这显然是荒谬的，笨拙的，所以我该怎么做才能解决这个问题问题？ （顺便说一句，同样的行为发生在subprocess.Popen()）。

Answer 1

与代码的问题：

import os 

for s in settings: 
    job_file = open("new_file_s.sh", "w") 
    job_file.write("stuff that depends on s") 
    os.system(command_that_runs_file_s) 

是你是不是收盘job_file，使文件仍处于打开状态（而不是刷新）当您运行的系统调用。

做job_file.close()，或更好：使用上下文管理器来确保文件关闭。

import os 

for s in settings: 
    with open("new_file_s.sh", "w") as job_file: 
     job_file.write("stuff that depends on s") 
    os.system(command_that_runs_file_s)