What's the difference between %s and %d in Python string formatting?

They are used for formatting strings. %s acts a placeholder for a string while %d acts as a placeholder for a number. Their associated values are passed in via a tuple using the % operator.

name = 'marcog'number = 42print '%s %d' % (name, number)

will print marcog 42. Note that name is a string (%s) and number is an integer (%d for decimal).

See https://docs.python.org/3/library/stdtypes.html#printf-style-string-formatting for details.

In Python 3 the example would be:

print('%s %d' % (name, number))

from python 3 doc

%d is for decimal integer

%s is for generic string or object and in case of object, it will be converted to string

Consider the following code

name ='giacomo'number = 4.3print('%s %s %d %f %g' % (name, number, number, number, number))

the out put will be

giacomo 4.3 4 4.300000 4.3

as you can see %d will truncate to integer, %s will maintain formatting, %f will print as float and %g is used for generic number

obviously

print('%d' % (name))

will generate an exception; you cannot convert string to number

%s is used as a placeholder for string values you want to inject into a formatted string.

%d is used as a placeholder for numeric or decimal values.

For example (for python 3)

print ('%s is %d years old' % ('Joe', 42))

Would output

Joe is 42 years old