Python将终端输出写入文件然后读取文件

Question

I'm having trouble writing the terminal output (all print statements) to a textfile then reading that textfile in the same script. I keep getting an I/O error if I close the program to finish writing to the file and then re-open the file to read it, or no output for the final print(file_contents) statement.

Here's my code:

import sys

filename = open("/Users/xxx/documents/python/dump.txt", 'r+')

filename.truncate()

sys.stdout = filename

print('Hello')

print('Testing')

filename.close()

with open("/Users/xxx/documents/python/dump.txt") as file:
    data = file.read()
    print(file)

Any suggestions would be great! I'm planning to use this to print output's from some longer scripts to a slack channel.

Thanks!

Answer 1

The error you get is:
IOError: [Errno 2] No such file or directory: '/Users/xxx/documents/python/dump.txt' because: file open mode r+ does not create a file. Use mode w like this:

You have to reattach stdout to console again to print in console.

import sys

filename = open('/Users/xxx/documents/python/dump.txt', 'w')

# filename.truncate()  # mode 'w' truncates file

sys.stdout = filename

print('Hello')

print('Testing')

filename.close()

# reattach stdout to console
sys.stdout = sys.__stdout__

with open('/Users/xxx/documents/python/dump.txt') as file:
    data = file.read()
    print(data)

will print:

Hello  
Testing

Answer 2

The problem is you redirect sys.stdout to filename , and then you close the file. Afterwards you can't print anything anymore, since the file is closed.

sys.stdout = filename
..
..
filename.close()

with open("/Users/xxx/documents/python/dump.txt") as file:
    data = file.read()
    print(file)

The last print statement tries to print output to sys.stdout , which is a closed file.

If you want to get the old behavior back, you need to keep a reference to sys.stdout . This will solve it:

sys_out = sys.stdout
sys.stdout = filename
..
..
filename.close()

sys.stdout = sys_out

with open("/Users/xxx/documents/python/dump.txt") as file:
    data = file.read()
    print(file)

Answer 3

import sys

filename = open("/Users/xxx/documents/python/dump.txt", 'w')

sys_out = sys.stdout sys.stdout = filename

print('Hello')

print('Testing')

print('Test')

filename.close()

sys.stdout = sys_out

with open("/Users/xxx/documents/python/dump.txt", 'r') as file: data = file.read() print(data)