Write text expander in Python

[perfringo]

str.translate is for replacing character for character, string or None. So 'δ' -> 'delta_low' is possible, but 'delta_low' -> 'δ' is not.

>>> mapping = str.maketrans({"δ": 'delta_low'})                                                                                            
>>> 'Some measurement with δ did get get wrong'.translate(mapping)                                                                         
'Some measurement with delta_low did get get wrong'
>>> mapping = str.maketrans({'delta_low': "δ"})                                                                                            
/../
ValueError: string keys in translate table must be of length 1

.maketrans documentation:

Character keys will be then converted to ordinals.
If there are two arguments, they must be strings of equal length, and
in the resulting dictionary, each character in x will be mapped to the
character at the same position in y.

.translate documentation:

Translation table, which must be a mapping of Unicode ordinals to Unicode ordinals, strings, or None.