The challenge
Given a string, you have to return a string in which each character (case-sensitive) is repeated once.
double_char("String") ==> "SSttrriinngg"
double_char("Hello World") ==> "HHeelllloo WWoorrlldd"
double_char("1234!_ ") ==> "11223344!!__ "
The solution in Python code
This can easily be done by looping through each character and appending it to a list, which we then join and return at the end:
def double_char(s):
out = []
for i in s:
out.append(i+""+i)
return "".join(out)
However, we could simplify this down to a single list comprehension:
def double_char(s):
return "".join([i+''+i for i in s])
Or go one step further:
def double_char(s):
return ''.join(c * 2 for c in s)
Test cases to validate our solution
test.assert_equals(double_char("String"),"SSttrriinngg")
test.assert_equals(double_char("Hello World"),"HHeelllloo WWoorrlldd")
test.assert_equals(double_char("1234!_ "),"11223344!!__ ")
