def sum_of_powers(end, power = 2, start = 1):
  return sum([(i) ** power for i in range(start, end + 1)])

sum_of_powers(10) # 385
sum_of_powers(10, 3) # 3025
sum_of_powers(10, 3, 5) # 2925

def key_of_min(d):
  return min(d, key = d.get)

key_of_min({'a':4, 'b':0, 'c':13}) # b

def print_x_pattern(size):
    i,j = 0,size - 1

    while j >= 0 and i < size:

        initial_spaces = ' '*min(i,j)
        middle_spaces = ' '*(abs(i - j) - 1)
        final_spaces = ' '*(size - 1 - max(i,j))

        if j == i:
            print(initial_spaces + '*' + final_spaces)
        else:
            print(initial_spaces + '*' + middle_spaces + '*' + final_spaces)

        i += 1
        j -= 1

print_x_pattern(7)

from collections import defaultdict

def combine_values(*dicts):
  res = defaultdict(list)
  for d in dicts:
    for key in d:
      res[key].append(d[key])
  return dict(res)
  
d1 = {'a': 1, 'b': 'foo', 'c': 400}
d2 = {'a': 3, 'b': 200, 'd': 400}

combine_values(d1, d2) # {'a': [1, 3], 'b': ['foo', 200], 'c': [400], 'd': [400]}

def print_pyramid_pattern(n):
     
    # outer loop to handle number of rows
    # n in this case
    for i in range(0, n):
     
        # inner loop to handle number of columns
        # values changing acc. to outer loop
        for j in range(0, i+1):
         
            # printing stars
            print("* ",end="")
      
        # ending line after each row
        print("\r")
 
print_pyramid_pattern(10)

# importing the modules
import os
import shutil

# getting the current working directory
src_dir = os.getcwd()

# printing current directory
print(src_dir) 

# copying the files
shutil.copyfile('test.txt', 'test.txt.copy2') #copy src to dst

# printing the list of new files
print(os.listdir())