Tuple and placeholder interaction with python print()?

Question

I have run below 4 sets of statements, and they give different result. I am unsure about the cause of the difference. Please see notes below -

Case1

'usercount' coerced to tuple, why does formatting work when it becomes a tuple? Is coerced the right term here?

usercount=(6)  #integer value
print ("Users connected: %d"%(usercount,))  
Users connected: 6

Case2

%s or %d makes no difference, if its a tuple, print function works the same way.

usercount=(6)
print ("Users connected: %s"%(usercount,))
Users connected: 6

Case3

'usercount' declared as tuple, print fxn works fine with %s placeholder.

usercount=(6,) # now tuple
print ("Users connected: %s"%(usercount,))
Users connected: (6,)

Case4

Same case %d placeholder throws an error, number required, not tuple.

usercount=(6,)
print ("Users connected: %d"%(usercount,))
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-59-02d2ce66d935> in <module>()
      1 usercount=(6,)
----> 2 print ("Users connected: %d"%(usercount,))
TypeError: %d format: a number is required, not tuple

Also, both placeholders work, when tuple declared the other way.

usercount=(6,)
print ("Users connected: %s"%(usercount))
Users connected: 6

usercount=(6,)
print ("Users connected: %d"%(usercount))
Users connected: 6

`(usercount)` does not declare a tuple. It is just `usercount` with parentheses around it. — Klaus D., May 08 '18 at 03:57

score 2 · Accepted Answer · answered May 08 '18 at 04:04

Its good to know that you should use %s for strings %d(decimal) for numbers, you can read this Link for getting better information about these two.
but in your cases:

Case1:

the usercount=(6) lines just returns an Integer value and its true way to use %d.

Case2:

the usercount=(6) lines just returns an Integer value and its can be casted to string and printed so you can use%s for that too.

Case3:

the usercount=(6,) lines just returns a Tuple value and its can be casted to string and printed so you can use%s for that too.

Case4:

the usercount=(6,) lines just returns a Tuple value and in this case you can not cast a tuple to an Integer so you cant use %d for that.

2

Thanks, this is succinct. – pyeR_biz May 08 '18 at 04:12