Write a program that allows the user to enter a nonnegative integer $k$ and returns the sum of the first $k$ perfect squares, $$\sum_1^k{k^2}.$$ For example, if $k=4$ the sum should be $1^2 + 2^2 + 3^2 + 4^2 = 1 + 4 + 9 + 16 = 30$. A sample execution might appear as

Enter k: 4
30

Solution:

k = int(input('Enter k: '))
total = 0
for j in range(1, k+1):
    total += j*j
print(total)

Ask the user for a word and then output the following pattern.

Enter word: example
e
ex
exa
exam
examp
exampl
example

Our first solution is an index-based loop which uses the index value to create an appropriate slice.

word = input('Enter a word: ')
for k in range(len(word)):
    print(word[ :1+k])

An alternative approach uses the more traditional loop over characters of the string, while maintaining a buffer that includes all characters seen thus far (and thus those that should be printed on the current line).

buffer = ''
word = input('Enter a word: ')
for c in word:
    buffer += c      # add new character to the line
    print(buffer)