str.isalpha() : checks whether the string consists of alphabetic characters only.

str.isdigit()?: checks whether the string consists of digits only.

str.islower():?

str.isupper()

str.center(width, fillchar) : returns centered in a string of length width. Padding is done using the specified fillchar. Default filler is a space.

def main():

s = input('Please enter a digit: ')

l = [int(s), int(s.center(2,s)), int(s.center(3,s)), int(s.center(4,s))]

total = sum(l)

print(int(s))

print(l)

print(total)

Result:

=============================exercise15.py =============================

Please enter a digit: 9

9

[9, 99, 999, 9999]

11106

>>>

=============================exercise15.py =============================

Please enter a digit: 1

1

[1, 11, 111, 1111]

1234

>>>

str.startswith()： checks whether the string starts with str, optionally restricting the matching with the given indices start and end.

Parameters：

str? This is the string to be checked.

beg? This is the optional parameter to set start index of the matching boundary.

end? This is the optional parameter to set start index of the matching boundary.

Return Value

This method returns true if found matching string otherwise false.

sample code;

'delimiter'.join(seq): The?join()method returns a string in which the string elements of sequence have been joined by str separator/delimiter.

>>> delimiter=''

>>> seq=['list1']

>>> seq2=['list2']

>>> delimiter.join(seq+seq2)

'list1list2'

>>> seq+seq2

['list1', 'list2']

Slicing and Reverse of string:

Slicing and Reversing