Quick Overview

This question evaluates proficiency in Python environment management, code comprehension and line-by-line explanation, algorithmic time and space complexity analysis, and unit testing and packaging practices (including docstrings and pytest).

Explain Python Virtual Environment Setup and Function Analysis

Company: Capital One

Role: Data Scientist

Category: Coding & Algorithms

Difficulty: medium

Interview Round: Onsite

##### Scenario Technical screen where candidate and interviewer jointly walk through Python code snippets used in a data-science repository. ##### Question Show how you would create, activate, and later remove a Python virtual environment on a Unix system. Given the following Python function (provided by interviewer), explain line-by-line what it does and its time/space complexity. Write unit tests that would fully cover edge cases for this function. ##### Hints Focus on correct CLI commands, Python packaging best practices, docstrings, pytest usage, and explaining algorithmic behavior clearly.

Quick Answer: This question evaluates proficiency in Python environment management, code comprehension and line-by-line explanation, algorithmic time and space complexity analysis, and unit testing and packaging practices (including docstrings and pytest).

You are given a sequence of shell-like commands that manage Python virtual environments on a Unix system. Validate the sequence according to these rules: - Allowed commands are exactly: "create NAME", "activate NAME", "deactivate", "remove NAME". - Initially, no environments exist and no environment is active. - create NAME: valid only if NAME does not already exist; then NAME is added to the set of environments. - activate NAME: valid only if NAME exists and no environment is currently active; then NAME becomes the active environment. - deactivate: valid only if an environment is currently active; then there is no active environment. - remove NAME: valid only if NAME exists and NAME is not the active environment; then NAME is removed from the set of environments. Return the 0-based index of the first invalid command. If all commands are valid, return -1.

Constraints

  • 1 <= len(commands) <= 100000
  • Each command is one of: 'create NAME', 'activate NAME', 'deactivate', 'remove NAME'
  • NAME consists of lowercase letters, digits, underscores, or hyphens; 1 to 32 characters
  • At most one environment can be active at any time
  • Return the index of the first invalid command or -1 if all are valid
  • Aim for O(n) time and O(n) space where n = len(commands)

Hints

  1. Track existing environments with a hash set and the active environment with a variable.
  2. Parse each command into tokens and validate arity (one or two tokens).
  3. Return immediately when a rule is violated to capture the first invalid index.

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