您应该同时使用python 2和3io.StringIO处理unicode对象以及io.BytesIO处理bytes对象，以实现前向兼容（这是3所提供的全部功能）。
这是一个更好的测试（针对python 2和3），其中不包括从numpy到str/的转换成本bytes
import numpy as np
import string
b_data = np.random.choice(list(string.printable), size=1000000).tobytes()
u_data = b_data.decode('ascii')
u_data = u'\u2603' + u_data[1:] # add a non-ascii character
接着：
import io
%timeit io.StringIO(u_data)
%timeit io.StringIO(b_data)
%timeit io.BytesIO(u_data)
%timeit io.BytesIO(b_data)
在python 2中，您还可以测试：
import StringIO, cStringIO
%timeit cStringIO.StringIO(u_data)
%timeit cStringIO.StringIO(b_data)
%timeit StringIO.StringIO(u_data)
%timeit StringIO.StringIO(b_data)
其中一些会崩溃，抱怨非ASCII字符
Python 3.5结果：
>>> %timeit io.StringIO(u_data)
100 loops, best of 3: 8.61 ms per loop
>>> %timeit io.StringIO(b_data)
TypeError: initial_value must be str or None, not bytes
>>> %timeit io.BytesIO(u_data)
TypeError: a bytes-like object is required, not 'str'
>>> %timeit io.BytesIO(b_data)
The slowest run took 6.79 times longer than the fastest. This Could mean that an intermediate result is being cached
1000000 loops, best of 3: 344 ns per loop
Python 2.7结果（在另一台机器上运行）：
>>> %timeit io.StringIO(u_data)
1000 loops, best of 3: 304 µs per loop
>>> %timeit io.StringIO(b_data)
TypeError: initial_value must be unicode or None, not str
>>> %timeit io.BytesIO(u_data)
TypeError: 'unicode' does not have the buffer interface
>>> %timeit io.BytesIO(b_data)
10000 loops, best of 3: 77.5 µs per loop
>>> %timeit cStringIO.StringIO(u_data)
UnicodeEncodeError: 'ascii' codec cant encode character u'\u2603' in position 0: ordinal not in range(128)
>>> %timeit cStringIO.StringIO(b_data)
1000000 loops, best of 3: 448 ns per loop
>>> %timeit StringIO.StringIO(u_data)
1000000 loops, best of 3: 1.15 µs per loop
>>> %timeit StringIO.StringIO(b_data)
1000000 loops, best of 3: 1.19 µs per loop
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