CODEWITHSUNDEEP
python-3.x
Max Hajkowicz
Max Hajkowicz

Reputation: 3

Is it possible to save result of "exec" into a text file python

When I do this I receive an error :

content = (open("to_be_intepreted.txt").read())
output = exec(content)
f = open("output.txt", "w")
f.write(output)
f.close()

Is there a way to achieve this? The error I receive is:

Write() argument must be str, not None

Upvotes: 0

Views: 607

Answers (2)

Roland Smith
Roland Smith

Reputation: 43495

You could run exec with new globals and locals dictionaries.

with open("to_be_intepreted.txt") as f:
    content = f.read()

loc, glob = {}, {}
exec(content, glob, loc)

The result should then be in one of the dictionaries, unless it has gone out of scope before exec ended.

Upvotes: 0

cwahls
cwahls

Reputation: 753

As @ApproachingDarknessFish points out, exec executes the code and returns None.

Therefore, it's not possible to save the result of exec to a file. However, there are two options:

  1. Redirect stdout to the output file.

    import sys
import traceback

# save a reference to the stdout
stdout_temp = sys.stdout

with open('to_be_interpreted.txt') as tbi, \
        open('output.txt', 'w') as out:
    # monkey-patch stdout (bad practice)
    sys.stdout = out
    try:
        # execute code using exec (bad practice)
        exec(tbi.read())
        # or rename to_be_interpreted.txt's extension to be .py and do
        # import to_be_interpreted
    except:
        # display any errors to the screen
        traceback.print_exc(file=stdout_temp)

    # flush stdout to write contents to file
    sys.stdout.flush()

    # reset stdout using reference
    sys.stdout = stdout_temp

    Monkey-patching a built-in module is a bad idea because it may have unintended consequences. However, you could keep the existing format of your to_be_interpreted file.

    In addition to security issues, consider replacing exec with import to_be_interpreted after changing the to_be_interpreted file's extension. Interpreting the code at runtime using import would let you know where errors are if any.

  2. Wrap the code to be interpreted inside a context.

    After opening the file, print the content directly to the output file.

    with open('output.txt', 'w') as fp:
    # start to-be-interpreted code
    print('string to print to output', file=fp)
    # end to-be-interpreted code

    The advantage is minimal code needs to change in your current script and the file closes automatically.

    The disadvantage is references to stdout in to_be_interpreted.txt need to be replaced with the file.

Comment if you have any questions,

Clay

Upvotes: 1

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