php's strtr for python

Question

php has the strtr function:

strtr(\'aa-bb-cc\', array(\'aa\' => \'bbz\', \'bb\' => \'x\', \'cc\' => \'y\'));
# bbz-x-y

It replace

Answer 1

str.translate is the equivalent, but can only map to single characters.

Answer 2

def strtr(strng, replace):
    if replace and strng:
        s, r = replace.popitem()
        return r.join(strtr(subs, dict(replace)) for subs in strng.split(s))
    return strng

j=strtr('aa-bb-cc', {'aa': 'bbz', 'bb': 'x', 'cc': 'y'})
assert j=='bbz-x-y', j

Answer 3

The answers on this thread are so out-dated. Here we go...

Option #1: Use the str.format() function to handle this:

"Hello there {first_name} {last_name}".format(first_name="Bob", last_name="Roy")

Option #2: Use the Template class

from string import Template
t = Template('Hello there $first_name $last_name')
t.substitute(first_name="Bob", last_name="Roy")

Reference: Python String Formatting Best Practices

Answer 4

Here is a naive algorithm:

Use an index to walk the original string character by character and check for each index whether one of the search strings is equal to the string from the current index on. If a match is found, push the replacement in a buffer and proceed the index by the length of the matched string. If no match is found, proceed the index by one. At the end, concatenate the strings in the buffer to a single string.

def strtr(strng, replace):
    buffer = []
    i, n = 0, len(strng)
    while i < n:
        match = False
        for s, r in replace.items():
            if strng[i:len(s)+i] == s:
                buffer.append(r)
                i = i + len(s)
                match = True
                break
        if not match:
            buffer.append(strng[i])
            i = i + 1
    return ''.join(buffer)

Answer 5

The following uses regular expressions to do it:

import re

def strtr(s, repl):
  pattern = '|'.join(map(re.escape, sorted(repl, key=len, reverse=True)))
  return re.sub(pattern, lambda m: repl[m.group()], s)

print(strtr('aa-bb-cc', {'aa': 'bbz', 'bb': 'x', 'cc': 'y'}))

Like the PHP's version, this gives preference to longer matches.