将字符串作为python代码执行并存储输出+错误

Question

I'm writing a small IDE for myself in Python at the moment and want to execute the text of my editor as Python code. I get the text of my editor as a string. I want to execute the code, save the ouput & errors in string-variables ( o and e ) and then I render the output in my IDE.

It works fine as long as I don't have any errors ( my_code ). Once I execute code containing an error ( my_code_with_error - commented below), it seems as if the code is not returning and "silently" crashing. In fact I even get Process finished with exit code 0 in Pycharm - probably because I switched sys.stdout for my own StringIO instance.

How can I execute the code-string, even if it has errors and then save the error / normal output in a variable as a String?

import sys
from io import StringIO

# create file-like string to capture output
codeOut = StringIO()
codeErr = StringIO()
print("Start")

my_code = """
print("Hello World!")
"""

my_code_with_error = """
print("Hello world!")
print(avfsd)  # error -> printing a variable that does not exist.
"""

print("Executing code...")
# capture output and errors
sys.stdout = codeOut
sys.stderr = codeErr

exec(my_code )  # this works fine
# exec(my_code_with_error)  # as soon as there is an error, it crashes silently.

# restore stdout and stderr
sys.stdout = sys.__stdout__
sys.stderr = sys.__stderr__
print("Finished code execution.")

e = codeErr.getvalue()
o = codeOut.getvalue()
print("Error: " + e)
print("Output: " + o)

codeOut.close()
codeErr.close()

PS: There was a really old question from 2009 where I got some of my code, but can't find any more recent questions concerning this topic. ( How do I execute a string containing Python code in Python? )

Answer 1

Try surrounding the execution code in a try/except block.

try:
    exec(my_code)
except:
    print("Unexpected error:", sys.exc_info()[0])
    raise

Answer 2

You can do that by catching the exceptions :

try:
    exec(my_code_with_error)
except Exception as e:
    print(e)

Raymond posted a similar answer as I was writting mine. Raymond's answer works in Python 2 also (see https://wiki.python.org/moin/HandlingExceptions , "General Error Handling" in "Questions") and has the advantage of outputing the error class too.