Explain this: print("%s"%1) outputs 1.

Question

How does this work?

Answer 1

% is string formating operator (when it is used with a string):
formatString % values

where
formatString - is a string with format specifiers like %s, %d...
values is a tuple that contains values to replace format specifiers in the format string.

"%s"%1
it is equal to
"%s" % (1,)
%s means put value converted to string
%s will be replaced with str(1), which is 1

for example:
v = 2.0
print("values of variable %s is %f"%("v", v))

will output
values of variable v is 2.000000

%s is replaced with string "v" (1st value)
and %f is replaced with floating point value of v (2nd value)