Given this code:
def double_char(str):
result = ""
for i in range(len(str)):
result += str[i] + str[i]
return result
Is result = "" the initialization of a string? If so, was it necessary to do in the first place?
-
1Note that this whole thing is rather inefficient; it's better to join a list than to build a string a character at a time since with immutable strings this means creating a new string object every iteration.Wooble– Wooble2014-01-23 04:59:21 +00:00Commented Jan 23, 2014 at 4:59
Add a comment
|
2 Answers
When you do
result += ...
it basically means that
result = result + ...
Python will not know the value result at this point. So, it will throw this error
UnboundLocalError: local variable 'result' referenced before assignment
Anyway, it is always better to initialize the variables.
Suggestions
Don't use
stras a variable name, it hides the builtinstrfunction.What you are trying to do, can be done in a single line, like this
return "".join(i*2 for i in input_string)
def double_char(input_string):
return "".join(i*2 for i in input_string)
print double_char("thefourtheye") # tthheeffoouurrtthheeyyee
Comments
While Python doesn't require you to state the type of a variable before using it (e.g. int a = 10 instead of just a = 10), it is necessary for the variable result to exist before += can be used with it. Otherwise when you use result += ... Python will try result = result + ....
As another suggestion, avoid naming a variable str since it overwrites the built-in str function/type in Python.
