python 2.7/exec/有什么问题？

Question

我的这段代码在 Python 2.5 中运行良好但在 2.7 中运行不正常:

import sys
import traceback
try:
    from io import StringIO
except:
    from StringIO import StringIO

def CaptureExec(stmt):
    oldio = (sys.stdin, sys.stdout, sys.stderr)
    sio = StringIO()
    sys.stdout = sys.stderr = sio
    try:
        exec(stmt, globals(), globals())
        out = sio.getvalue()
    except Exception, e:
        out = str(e) + "\n" + traceback.format_exc()
    sys.stdin, sys.stdout, sys.stderr = oldio
    return out

print "%s" % CaptureExec("""
import random
print "hello world"
""")

然后我得到:

string argument expected, got 'str'
Traceback (most recent call last):
  File "D:\3.py", line 13, in CaptureExec
    exec(stmt, globals(), globals())
  File "", line 3, in 
TypeError: string argument expected, got 'str'

Answer 1

io.StringIO 在 Python 2.7 中令人困惑，因为它是从 3.x 字节/字符串世界向后移植的。此代码与您的错误相同:

from io import StringIO
sio = StringIO()
sio.write("Hello\n")

原因:

Traceback (most recent call last):
  File "so2.py", line 3, in <module>
    sio.write("Hello\n")
TypeError: string argument expected, got 'str'

如果您只使用 Python 2.x，则完全跳过 io 模块，并坚持使用 StringIO。如果您真的想使用 io，请将导入更改为:

from io import BytesIO as StringIO