python - translate and maketrans

>>> mystring='these'
>>> string.maketrans('ts','75')
'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\
x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !"#$%&\'()*+,-./0123456789:;<=>?@ABC
DEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqr57uvwxyz{|}~\x7f\x80\x81\x82\x83
\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97
\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab
\xac\xad\xae\xaf\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf
\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3
\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7
\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb
\xfc\xfd\xfe\xff'
>>> transtbl=string.maketrans('ts','75')
>>>
>>> mystring
'these'
>>> mystring.translate(transtbl)
'7he5e'
>>>
>>>
>>> mystring
'these'
>>> mystring.translate(None,'ts')
'hee'
>>>

To translate mystring we need a translate table which has to be 256 bytes long. So we will use maketrans to cook up that table for us.

syntax: string.maketrans("From","to")

Just use this table in translate function.

syntax: mystringhere.translate("translation table")

Also, translate can be used without a translation table. If we give translation table as "None" and then provide optional list, these listed characters will be deleted.

The latter way of translate can come handy if you want to check if an incoming string contains numbers.

e.g.

>>> mystring='ab1234'
>>> if len(mystring.translate(None,'0123456789')) < len(mystring) :
... print 'input string contains numbers'
...
input string contains numbers

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