Use Hash value in python code #memo

Recently when I reading a code and test it, the code didn’t work. ;( The code used python hash function for generating some values. This is the reason why the code didn’t work in python3. Python3 hash function returns same value in only same session.

So it should not use as permanent value. For example…

$ python -c "print(hash('a'));"
-6739920846501962706

$ python -c "print(hash('a'));"
2223204068672557918

Now I god different value from same string object ‘a’. Next, I used hashlib.

$ python -c "import hashlib;m=hashlib.md5(b'a').digest();print(m)"
b'\x0c\xc1u\xb9\xc0\xf1\xb6\xa81\xc3\x99\xe2iw&a

$ python -c "import hashlib;m=hashlib.md5(b'a').digest();print(m)"
b'\x0c\xc1u\xb9\xc0\xf1\xb6\xa81\xc3\x99\xe2iw&a

Next I could got same hashed value from binary object.

To get same value with hash() function for testing, set PYTHONHASHSEED value in environment value is required. https://docs.python.org/3.7/using/cmdline.html?highlight=hashseed#envvar-PYTHONHASHSEED

$ export PYTHONHASHSEED=0
$ python -c "print(hash('a'));"
-7583489610679606711
$ python -c "print(hash('a'));"
-7583489610679606711

It just memorandum for me….

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