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Python Data Structures and Algorithms - Recursion: Factorial of a non-negative integer

Python Recursion: Exercise-4 with Solution

Write a Python program to get the factorial of a non-negative integer.

Sample Solution:

Python Code:

def factorial(n):
  if n <= 1:
    return 1
  else:
    return n * (factorial(n - 1))
    
print(factorial(5))

Sample Output:

120

Flowchart:

Flowchart: Recursion: Factorial of a non-negative integer.

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Python: Tips of the Day

Find current directory and file's directory:

To get the full path to the directory a Python file is contained in, write this in that file:

import os 
dir_path = os.path.dirname(os.path.realpath(__file__))

(Note that the incantation above won't work if you've already used os.chdir() to change your current working directory, since the value of the __file__ constant is relative to the current working directory and is not changed by an os.chdir() call.)

To get the current working directory use

import os
cwd = os.getcwd()

Documentation references for the modules, constants and functions used above:

  • The os and os.path modules.
  • The __file__ constant
  • os.path.realpath(path) (returns "the canonical path of the specified filename, eliminating any symbolic links encountered in the path")
  • os.path.dirname(path) (returns "the directory name of pathname path")
  • os.getcwd() (returns "a string representing the current working directory")
  • os.chdir(path) ("change the current working directory to path")

Ref: https://bit.ly/3fy0R6m