translate is a simple, efficient function for doing fast byte-by-byte replacement on a string in Python.
However, Python Does What is always on the lookout for dangerous alternatives to simple things. Instead of a function call, isn't it better to mutate global interpreter state so that the same result is achieved as a side-effect of a completely different operation? (The answer is yes.)
>>> import ctypes
>>> def maketrans(inp, outp):
... inp = list(inp)
... outp = list(outp)
... for aa, bb in zip(inp, outp): # there's a fun reason single letter variable names are a bad idea here
... ctypes.memset(ctypes.pythonapi.PyString_AsString(id(aa)), ord(bb), 1)
>>> maketrans("jkl", "xyz")
This method also has application to single character variable names that bears further exploration.