Single Element Tuple

Phenomena

In [18]: (3 + 4)
Out[18]: 7

In [19]: (3 + 4, )
Out[19]: (7,)

Reason

In [20]: (3 + 4) * 5
Out[20]: 35

or

In [21]: (3 + 4) * 5
Out[21]: (7, 7, 7, 7, 7)

References

[1] Bugs@Python, Make Python create a tuple with one element in a clean way