LESSON 369 OF 410 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: cat v1 — Print Lines in Python

Practice

Build a tiny version of the Unix cat command. Given a list of lines, return them joined by newline characters (\n) so they print one per line.

Lines can be blank, and the list can be empty (the result is then an empty string).

Function signature:

def cat(self, lines: List[str]) -> str:

Example:

Input: lines = ["hello", "world", "foo"]

Output: "hello\nworld\nfoo"

When printed:
hello
world
foo

Think of the output as one big string where each input line is separated from the next by a newline character. You don't need to loop and concatenate manually — Python has a built-in helper for this.

Use the string method "\n".join(lines) — this glues every element of lines together with "\n" in between.

The full solution is a one-liner:

class Solution:
    def cat(self, lines):
        return "\n".join(lines)

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CLI Tool: cat v1 — Print Lines in Python

Cat V1 in Python