How to Perform Multiple String Replacements Efficiently Using a Dictionary in Python?

Multiple String Replacements with a Dictionary

In many programming scenarios, it becomes necessary to replace specific words or phrases within a string using values from a dictionary. To address this challenge, there are several approaches that utilize Python's powerful string manipulation capabilities.

One effective method involves employing the re module:

<code class="python">import re

s = 'Спорт russianA'
d = {'Спорт': 'Досуг', 'russianA': 'englishA'}

keys = (re.escape(k) for k in d.keys())
pattern = re.compile(r'\b(' + '|'.join(keys) + r')\b')
result = pattern.sub(lambda x: d[x.group()], s)</code>

This code utilizes the re.compile() function to create a regular expression (regex) pattern that matches the keys of the dictionary as whole words. The re.escape() function is used to prevent any special characters in the keys from interfering with the regex syntax.

Once the pattern is created, it is applied to the string s using the sub() method. The lambda function passed to sub() extracts the matched key from the regular expression match object (x) and replaces it with the corresponding value from the dictionary (d[x.group()]). The resulting string is stored in the result variable.

In this example, the output would be 'Досуг englishA', as the words 'Спорт' and 'russianA' in the string 'Спорт russianA' are replaced with their values from the dictionary.

It is important to note that the regex pattern created in this approach matches whole words only. If you require matching substrings within words, a different pattern can be used:

<code class="python">pattern = re.compile('|'.join(re.escape(k) for k in d.keys()))</code>

However, in this scenario, you should ensure that the dictionary keys are sorted in descending order by length to prevent substrings from being matched incorrectly.

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