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Models a pseudo random function (a PRF).
The numbers are based on a SHA1 hash of the initial key.
Each PRF is created based on a key (which should be random and secret) and a maximum (which may be public):
>>> f = PRF("some random key", 256)
Calling f return values between zero and the given maximum:
>>> f(1) 26L >>> f(2) 69L >>> f(3) 217L






Inherited from 


Inherited from 

Create a PRF keyed with the given key and max. The key must be a string whereas the max must be a number. Output value will be in the range zero to max, with zero included and max excluded. To make a PRF what generates numbers less than 1000 do: >>> f = PRF("key", 1000) The PRF can be evaluated by calling it on some input: >>> f("input") 327L Creating another PRF with the same key gives identical results since f and g are deterministic functions, depending only on the key: >>> g = PRF("key", 1000) >>> g("input") 327L We can test that f and g behave the same on many inputs: >>> [f(i) for i in range(100)] == [g(i) for i in range(100)] True Both the key and the max is used when the PRF is keyed. This means that >>> f = PRF("key", 1000) >>> g = PRF("key", 10000) >>> [f(i) for i in range(100)] == [g(i) for i in range(100)] False

Return a number based on input. If the input is not already a string, it is hashed (using the normal Python hash builtin) and the hash value is used instead. The hash value is a 32 bit value, so a string should be given if one wants to evaluate the PRF on more that 2**32 different values. >>> prf = PRF("key", 1000) >>> prf(1), prf(2), prf(3) (501L, 432L, 133L) Since prf is a function we can of course evaluate the same input to get the same output: >>> prf(1) 501L The prf can take arbitrary input: >>> prf(("input", 123)) 284L Nonstring input will be converted with str, which means that the input must have a deterministic __str__ method. This means that hashable instances are probably best. 
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