如何在 Python 中擷取腳本 stdout 輸出？

Capturing stdout Output from Scripts in Python

When working with external scripts, it often becomes necessary to capture their stdout output for further processing. A common approach is to use the write() function to print the output, which can then be stored in a variable. However, this approach doesn't always work, as exemplified by the following script:

<code class="python"># module writer.py
import sys

def write():
    sys.stdout.write("foobar")</code>

To capture the output of the write() function, a solution involving the cStringIO module was proposed:

<code class="python">import sys
from cStringIO import StringIO

# setup the environment
backup = sys.stdout

# ####
sys.stdout = StringIO()     # capture output
write()
out = sys.stdout.getvalue() # release output
# ####

sys.stdout.close()  # close the stream 
sys.stdout = backup # restore original stdout

print out.upper()   # post processing</code>

However, there are more efficient and Pythonic ways to achieve this goal:

Using contextlib.redirect_stdout (Python 3.4+)

This method utilizes the contextlib.redirect_stdout context manager to temporarily redirect stdout output to a StringIO object:

<code class="python">from contextlib import redirect_stdout
import io

f = io.StringIO()
with redirect_stdout(f):
    help(pow)
s = f.getvalue()</code>

Using io.StringIO directly

Another approach is to directly create a StringIO object and manually route stdout output to it:

<code class="python">import io

output = io.StringIO()
sys.stdout = output
write()
sys.stdout.seek(0)
captured_output = output.read()</code>

By implementing these methods, developers can effectively capture and process script output without resorting to complex workarounds.

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