>>> print(3 + 4)
7
>>> 3 + 4
Out[1]: 7
>>> def printSum(a, b):
...    print(a + b)
...    
>>> printSum(3, 4)
7
>>> def doSum(a, b):
...    return a + b
...
>>> doSum(3, 4)
Out[1]: 7
>>> type(7)
Out[1]: int
>>> type(7.3)
Out[1]: float
>>> type(5 / 2)
Out[1]: int
>>> type(5 / 2.)
Out[1]: float
>>> type(doSum(3, 4))
Out[1]: int
>>> type(doSum)
Out[1]: function
>>> type(printSum)
Out[1]: function
>>> type(printSum(3, 4))
7
Out[1]: NoneType
>>> doSum(3, 4) + doSum(5, 6)
Out[1]: 18
>>> doSum(doSum(3, 4), doSum(5, 6))
Out[1]: 14
>>> printSum(3, 4) + printSum(5, 6)
7
11
Traceback (most recent call last):
  File "/Applications/Canopy.app/appdata/canopy-1.1.0.1371.macosx-x86_64/Canopy.app/Contents/lib/python2.7/site-packages/IPython/core/interactiveshell.py", line 2803, in run_code
    exec code_obj in self.user_global_ns, self.user_ns
  File "<ipython-input-1-4e88823d760c>", line 1, in <module>
    printSum(3, 4) + printSum(5, 6)
TypeError: unsupported operand type(s) for +: 'NoneType' and 'NoneType'
>>> doSum(3, 4)
Out[1]: 7
>>> x = doSum(3, 4)
>>> x
Out[1]: 7
>>> type(x)
Out[1]: int
>>> x = 7.3
>>> type(x)
Out[1]: float
>>> x = 7.0
>>> type(x)
Out[1]: float
>>> x = int(x)
>>> type(x)
Out[1]: int