Dev Nest Guide
pythonintermediate10 minutes

Predict the Output: List and Dictionary Comprehension Logic

Analyze the given Python code containing nested list and dictionary comprehensions along with conditional logic, and predict the exact output it produces.

Challenge prompt

Given the Python code below, carefully read through the nested list and dictionary comprehensions and internal logic. Predict what the output will be when the code is executed. Explain your reasoning if asked, but for now, only provide the exact printed output: python result = {i: [j**2 if j % 2 == 0 else j**3 for j in range(i)] for i in range(5)} print(result)

Guidance

  • • Break down the comprehension step-by-step: start with the outer dictionary comprehension and analyze what keys and values it produces.
  • • Focus on the inner list comprehension and understand how it transforms the list of numbers for each key.
  • • Pay attention to the conditional inside the list comprehension and how it changes the value depending on even or odd numbers.

Hints

  • • Recall that i in the outer comprehension goes from 0 to 4 inclusive, creating dictionary keys.
  • • Examine carefully what happens when i is 0—what would range(0) return?
  • • For list elements, even j values are squared (j**2), odd j values are cubed (j**3).

Starter code

result = {i: [j**2 if j % 2 == 0 else j**3 for j in range(i)] for i in range(5)}
print(result)

Expected output

{0: [], 1: [0], 2: [0, 1], 3: [0, 1, 4], 4: [0, 1, 4, 27]}

Core concepts

dictionary comprehensionlist comprehensionconditional expressionsloops

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