AttributeError: type object '_io.StringIO' has no attribute 'StringIO'

python2导入StringIO模块，直接：

from StringIO import StringIO

对于python3，StringIO和cStringIO模块已经没了，如果要使用的话，需要导入io模块：

from io import StringIO
dot_data = StringIO()

你也可以导入six模块来使用StringIO:

from six import StringIO

或

from sklearn.externals.six import StringIO  

例子：对于python2和python3都兼容：

try:
    from StringIO import StringIO
except ImportError:
    from io import StringIO

REF.

[1]http://stackoverflow.com/questions/11914472/stringio-in-python3

[2]https://github.com/pgbovine/OnlinePythonTutor/issues/111

see What’s New In Python 3.0