Swap first and last letter of a string in Python -

I hope I am clarifying something here, but I was playing with Python codingbat site, and the problem Found:

has been passed for a string, swap it with your first and last characters, if the length of the string is greater than 1.

I have come up with a single line solution that I thought would be sufficient, but coding.Bat has refused to accept it, with an index class error.

I played in IWEE (64 bit window edition) and I boiled down the problem:

  lane (str)   
 The odd problem is that  str = ''  returns:  
  'doh / doh'   
 This lane is not ('') should not be in the form of 0, but  str = 'a'  returns:  
  'a'   
 and  str = 'abc'  returns:  
  Doh abc / doh '  
 I expected ...  
 So my question is really; Why is the "lane" being examined for the turnarial operator or status, but the <0> len ('')  running on the console return 0, which is clearly less than 2?  
  Edit:   
 This solution actually works, however:  
  def front_back (str): If len (str) & lt; 2: Return Strength: Return str [-1] + str [1: -1] + str [0]   
 to 'mtadd'; Thank you for your reply, but it is not logical and / or it is a dragon ternary operator:  
  return (statement) and & lt; Statement was correct & gt; Or & lt; Statement is false & gt;   
 This is similar to C #:  
  return statement? TrueValue: falseValue;    
 
 
 It's a matter of.  
 Expression, the inherent order is as follows:  
  ((lenan (str) <2) and str) or ('doh' + str + '/ doh ')   
 In the case of  str = "" ,  lane (str) & lt; 2 evaluates  true , but  str , an empty string,  incorrect , thus  and  Expression is  , therefore the correct operation of  or  binary opus becomes the result of expression.  
  str = "ABC" ,  lane (str) & lt; 2  is  incorrect , therefore the expression  and  as the short-circuit  incorrect , and the expression on the right side of  or < / Code> results.  
  str = "ab" ,  len (str) & lt; 2  is true, so the  and  expression  or  binary operator passes its right operand, and since  bool ("ab") == true The value of ,  str  becomes the result of expression.  
 As you can see,  and  /  or  will not work with triangle operators of other languages ​​if the result of your code is  True  condition is equal to  False , for example  true and 0 or 1  yield  1 , while  0 is used True while doing second 1  yields  0 .  
 I recommend using Python's Thread if / other expression, such as:  
  str if len (str) & lt; 2 other 'die' + str + '/ dom'