implicitly concats of adjacent strings does not work with format

Wed Apr 29 09:14:59 EDT 2015

On 04/29/2015 08:42 AM, Cecil Westerhof wrote:
> I have the folowing print statements:
> print(
> 'Calculating fibonacci_old, fibonacci_memoize and '
> 'fibonacci_memoize once for {0} '.format(large_fibonacci))
>>> print(
> 'Calculating fibonacci_old, fibonacci_memoize and '
> 'fibonacci_memoize once for {0} '.format(large_fibonacci) +
> 'to determine speed increase')
>> print(
> 'Calculating fibonacci_old, fibonacci_memoize and '
> 'to determine speed increase'
> 'fibonacci_memoize once for {0} '.format(large_fibonacci))
>>> print(
> 'Calculating fibonacci_old, fibonacci_memoize and '
> 'fibonacci_memoize once for {0} '.format(large_fibonacci)
> 'to determine speed increase')
>> The first three work, but the last gives:
> 'to determine speed increase')
> ^
> SyntaxError: invalid syntax
>> Not very important, because I can use the second one, but I was just
> wondering why it goes wrong.
>
Adjacent string literals are concatenated. But once you've called a 
method (.format()) on that literal, you now have an expression, not a 
string literal.
You could either change the last line to
 + 'to determine speed increase')
or you could concatenate all the strings before calling the format method:
 print(
 'Calculating fibonacci_old, fibonacci_memoize and '
 'fibonacci_memoize once for {0} '
 'to determine speed increase' .format(large_fibonacci))
Something you may not realize is that the addjacent-concatenation occurs 
at compile time, so your third example could be transformed from:
 print(
 'Calculating fibonacci_old, fibonacci_memoize and '
 'to determine speed increase'
 'fibonacci_memoize once for {0} '.format(large_fibonacci))
to:
 print(
 'Calculating fibonacci_old, fibonacci_memoize and '
 'to determine speed increase'
 'fibonacci_memoize once for {0}'
 ' '.format(large_fibonacci))
All three literals are combined before format() is called. Knowing this 
could be vital if you had {} elsewhere in the 9single) literal.
-- 
DaveA