Why is hash() slower under python3.4 vs python2.7

Question

I was doing some performance evaluation using timeit and discovered a performance degredation between python 2.7.10 and python 3.4.3. I narrowed it down to the hash()<

Answer 1

There are two changes in hash() function between Python 2.7 and Python 3.4

1. Adoptions of SipHash
2. Default enabling of Hash randomization

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References:

• Since from Python 3.4, it uses SipHash for it's hashing function. Read: Python adopts SipHash
• Since Python 3.3 Hash randomization is enabled by default. Reference: object.__hash__ (last line of this section). Specifying PYTHONHASHSEED the value 0 will disable hash randomization.