使用Python subprocess.call()时如何写入文件开头？

Question

我运行以下脚本：

with open("logfile.txt", 'w') as log_file:
    cmd = path + '/somebinary'
    log_file.write("Running the command: %s\n" % cmd)
    subprocess.call(cmd, shell=True, stdout=log_file, stderr=log_file)

但是， cmd变量被写入文件的末尾而不是开头（这是我期待/希望的）。 有人可以向我解释为什么以及如何防止这种情况吗？

Answer 1

我想出了一个这样做的想法，也许你会发现它很有用。

输入：text.txt

123
lol
stack
overflow

代码

'''First I read the content of existing file and i append the first line of it to the text i want to appear in beginning'''
with open("text.txt", "r") as f:
    existing_lines = f.readlines()
    text_to_append = "Test"
    existing_lines[0] = text_to_append+"\n"+existing_lines[0]
'''And here I wite to the file'''
with open("text.txt", "w") as f:
    f.writelines(existing_lines)

Output：text.txt

Test
123
lol
stack
overflow

您可以在 text_to_append 中放置任何内容，只要它的字符串。