LESSON 393 OF 410 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: tr v1 — Single Char Swap in Python

Practice

Build a tiny version of the Unix tr command. Given a list of lines and two single characters fromChar and toChar, replace every occurrence of fromChar with toChar in each line, then return the lines joined by newline characters (\n).

Notes: fromChar and toChar are single ASCII characters, taken literally (no escapes like \, no ranges). Upper and lower case are different characters. A line may be empty, and may not contain fromChar at all.

Function signature:

def tr(self, lines: List[str], fromChar: str, toChar: str) -> str:

Example:

Input: lines = ["banana", "apple"], fromChar = "a", toChar = "X"

Output: "bXnXnX\nXpple"

When printed:
bXnXnX
Xpple

Use Python's built-in string method replace(old, new) on each line, then join with "\n".

The full solution:

class Solution:
    def tr(self, lines, fromChar, toChar):
        result = []
        for line in lines:
            result.append(line.replace(fromChar, toChar))
        return "\n".join(result)

STEP 1 OF 4

Guided

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CLI Tool: tr v1 — Single Char Swap in Python

Tr V1 in Python