python: get the print output in an exec statement
Since Python 3.4 there is a solution is the stdlib: https://docs.python.org/3/library/contextlib.html#contextlib.redirect_stdout
from io import StringIO
from contextlib import redirect_stdout
f = StringIO()
with redirect_stdout(f):
help(pow)
s = f.getvalue()
In older versions you can write a context manager to handle replacing stdout:
import sys
from io import StringIO
import contextlib
@contextlib.contextmanager
def stdoutIO(stdout=None):
old = sys.stdout
if stdout is None:
stdout = StringIO()
sys.stdout = stdout
yield stdout
sys.stdout = old
code = """
i = [0,1,2]
for j in i :
print j
"""
with stdoutIO() as s:
exec(code)
print("out:", s.getvalue())
You can redirect the standard output to a string for the duration of the exec call:
Python2
import sys
from cStringIO import StringIO
code = """
i = [0,1,2]
for j in i:
print(j)
"""
old_stdout = sys.stdout
redirected_output = sys.stdout = StringIO()
exec(code)
sys.stdout = old_stdout
print(redirected_output.getvalue())
Python3
import sys
from io import StringIO
code = """
i = [0,1,2]
for j in i:
print(j)
"""
old_stdout = sys.stdout
redirected_output = sys.stdout = StringIO()
exec(code)
sys.stdout = old_stdout
print(redirected_output.getvalue())
Here is Py3-friendly version of @Jochen's answer. I also added try-except
clause to recover in case of errors in the code
.
import sys
from io import StringIO
import contextlib
@contextlib.contextmanager
def stdoutIO(stdout=None):
old = sys.stdout
if stdout is None:
stdout = StringIO()
sys.stdout = stdout
yield stdout
sys.stdout = old
code = """
i = [0,1,2]
for j in i :
print(j)
"""
with stdoutIO() as s:
try:
exec(code)
except:
print("Something wrong with the code")
print("out:", s.getvalue())