String Translate using Dict - Python

In Python, translating a string based on a dictionary involves replacing characters or substrings in the string with corresponding values from a dictionary. For example, if we have a string "python" and a dictionary {"p": "1", "y": "2"}, we can translate the string to "12thon". Let’s explore a few methods to translate strings using dictionaries.

Using str.translate()

translate() method in Python allows for efficient string translation by using a translation table created from a dictionary. This method works well when replacing characters in a string.

# Input string and dictionary
a = "python"
b = {"p": "1", "y": "2"}

# Creating translation table from dictionary
trans = str.maketrans(b)

# Translating the string using the table
c = a.translate(trans)

print(c)

12thon

Explanation:

• The str.translate() method converts the dictionary into a translation table.
• The translate() method uses this table to replace characters in the string.
• This method is very efficient for character replacements.

Using loop and str.replace()

If we need to replace multiple substrings in a string based on a dictionary, we can use a for loop and the replace() method for each key-value pair in the dictionary.

# Input string and dictionary
a = "python"
b = {"p": "1", "y": "2"}

# Looping through the dictionary to replace characters
for k, v in b.items():
    a = a.replace(k, v)

print(a)

12thon

Explanation:

• We loop through each key-value pair in the dictionary.
• For each pair, the replace() method is called on the string to replace occurrences of the key with the corresponding value.
• This method is simple but less efficient than translate() for large strings or many replacements.

Using List Comprehension

List comprehension can be used to iterate through the string and apply the dictionary mappings to each character. This method is similar to using a loop but more compact.

# Input string and dictionary
a = "python"
b = {"p": "1", "y": "2"}

# Using list comprehension to translate string
c = ''.join([b.get(i, i) for i in a])

print(c)

12thon

Explanation:

• List comprehension iterates over each character in the string.
• The get() method is used to check if a character exists in the dictionary. If it does, it replaces it; otherwise, it keeps the character as is.

Using reduce()

The reduce() function from the functools module can also be used to apply a dictionary mapping to a string. It is more functional and can be used when we need to accumulate the result of applying the dictionary's values to each character.

from functools import reduce

# Input string and dictionary
a = "python"
b = {"p": "1", "y": "2"}

# Using reduce to apply replacements
c = reduce(lambda x, y: x.replace(y, b.get(y, y)), b.keys(), a)

print(c)

12thon

Explanation:

• The reduce() function applies the replace() method to the string for each key in the dictionary.
• The get() method ensures that characters not in the dictionary are not replaced.