can you write a str.replace() using dictionary values in Python?

Solution 1:

address = "123 north anywhere street"

for word, initial in {"NORTH":"N", "SOUTH":"S" }.items():
    address = address.replace(word.lower(), initial)
print address

nice and concise and readable too.

Solution 2:

you are close, actually:

dictionary = {"NORTH":"N", "SOUTH":"S" } 
for key in dictionary.iterkeys():
    address = address.upper().replace(key, dictionary[key])

Note: for Python 3 users, you should use .keys() instead of .iterkeys():

dictionary = {"NORTH":"N", "SOUTH":"S" } 
for key in dictionary.keys():
    address = address.upper().replace(key, dictionary[key])

Solution 3:

One option I don't think anyone has yet suggested is to build a regular expression containing all of the keys and then simply do one replace on the string:

>>> import re
>>> l = {'NORTH':'N','SOUTH':'S','EAST':'E','WEST':'W'}
>>> pattern = '|'.join(sorted(re.escape(k) for k in l))
>>> address = "123 north anywhere street"
>>> re.sub(pattern, lambda m: l.get(m.group(0).upper()), address, flags=re.IGNORECASE)
'123 N anywhere street'
>>>

This has the advantage that the regular expression can ignore the case of the input string without modifying it.

If you want to operate only on complete words then you can do that too with a simple modification of the pattern:

>>> pattern = r'\b({})\b'.format('|'.join(sorted(re.escape(k) for k in l)))
>>> address2 = "123 north anywhere southstreet"
>>> re.sub(pattern, lambda m: l.get(m.group(0).upper()), address2, flags=re.IGNORECASE)
'123 N anywhere southstreet'

Solution 4:

You are probably looking for iteritems():

d = {'NORTH':'N','SOUTH':'S','EAST':'E','WEST':'W'}
address = "123 north anywhere street"

for k,v in d.iteritems():
    address = address.upper().replace(k, v)

address is now '123 N ANYWHERE STREET'

Well, if you want to preserve case, whitespace and nested words (e.g. Southstreet should not converted to Sstreet), consider using this simple list comprehension:

import re

l = {'NORTH':'N','SOUTH':'S','EAST':'E','WEST':'W'}

address = "North 123 East Anywhere Southstreet    West"

new_address = ''.join(l[p.upper()] if p.upper() in l else p for p in re.split(r'(\W+)', address))

new_address is now

N 123 E Anywhere Southstreet    W

Solution 5:

"Translating" a string with a dictionary is a very common requirement. I propose a function that you might want to keep in your toolkit:

def translate(text, conversion_dict, before=None):
    """
    Translate words from a text using a conversion dictionary

    Arguments:
        text: the text to be translated
        conversion_dict: the conversion dictionary
        before: a function to transform the input
        (by default it will to a lowercase)
    """
    # if empty:
    if not text: return text
    # preliminary transformation:
    before = before or str.lower
    t = before(text)
    for key, value in conversion_dict.items():
        t = t.replace(key, value)
    return t

Then you can write:

>>> a = {'hello':'bonjour', 'world':'tout-le-monde'}
>>> translate('hello world', a)
'bonjour tout-le-monde'