如何在Python 3中比较numpy字符串

Question

The following demonstrates the problem:

import io
import numpy as np

a = np.loadtxt(io.StringIO("val1 val2\nval3 val4"), \
               dtype=np.dtype([("col1", "S10"), ("col2", "S10")]))
print("looks weired: %s"%(a["col1"][0]))
assert(a["col1"][0] == "val1")

I don't understand how I should compare the strings. On my system (numpy 1.6.2, python 3.2.2) the output looks like this:

>>> 
looks weired: b'val1'
Traceback (most recent call last):
  File "D:/..../bug_sample.py", line 7, in <module>
    assert(a["col1"][0] == "val1")
AssertionError

Answer 1

This is not numpy -related:

>>> b"asd" == "asd"
False

In Python 3 bytes objects don't compare equal to string s. So either:

• compare against b"val1" instead of "val1" so that the types match,
• decode the bytes object into a string (like .decode('utf-8') and compare with "val1" .