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Problem 6. (Fibonacci Number) Write a program fibonacci.py that accepts n (int) as command-line argument, and writes to standard output the nth number from the Fibonacci sequence (1, 1, 2, 3, 5, 8, 13, . . . ).



Answer :

teobguan2019

Answer:

  1. import sys
  3. def fibonacci(n):
  4.    if(n == 0 or n == 1):
  5.        return n  
  6.    else:
  7.        return fibonacci(n - 2) + fibonacci(n-1)
  9. num = int(sys.argv)  
  10. output = ""
  12. for i in range(1, num+1):
  13.    output += str(fibonacci(i)) + " "  
  15. print(output)

Explanation:

Firstly, we import sys module as we need to accepts n as command line argument (Line 1).

Next, create a function fibonacci takes take one input n (Line 3). If the n is zero or one, return the n itself (Line 4-5). Otherwise, the program shall run the recursive call to the fibonacci function itself by putting n-2 and n-1 as function argument, respectively (Line 6-7).

After that, use the sys.argv to get the command line argument and assign the value to num (Line 9).

Use a for loop to generate the output string by progressively calling the fibonacci function and join the return result to the output string (Line 12-13).

At last print the output string (Line 15).