使用％和变量名在python中打印变量

Question

I am currently learning python and would like to know how these two print statements are different? I mean both perform the same action but only differ in the syntax. Are there any other differences?

a = 5
b = 'hi'

print "The number is", a, " and the text is", b

print "The number is %d and the text is %s" %(a, b)

Answer 1

Well, the second one will fail if the variable a is not a number.

>>> a='hi'
>>> b='hi'
>>> print "The number is %d and the text is %s" %(a, b)
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-3-aa94a92667a1> in <module>()
----> 1 print "The number is %d and the text is %s" %(a, b)

TypeError: %d format: a number is required, not str

If a is always a number, they would behave very much alike, except the %d in the format forces it to be an integer, so if you have:

>>> a=1.2
>>> b='hi'
>>> print "The number is %d and the text is %s" %(a, b)
The number is 1 and the text is hi

You can see that it converts the number 1.2 to an integer 1 .

As per the comments, another option is to use the format function , that behaves similar to your first option but using a format string :

>>> a=1.2
>>> b='hi'
>>> print "The number is {} and the text is {}".format(a, b)
The number is 1.2 and the text is hi

It also allows to use named arguments:

>>> print "The number is {number} and the text is {text}".format(number=a, text=b)
The number is 1.2 and the text is hi