Python 3 Tutorial

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Python function return types

       return statement can be used to a pass control back to the caller or value from any Python function.

• return statement without a value

   Python return statement without a value return None Type .

• return statement with a value

   Python return statement return any valid type data to the caller

Python Function returns None in following cases.

• Phython function uses a return without a value
• or no return statement

Following Nothing function has empty body. checking return type of the function gives 'NoneType'

      		def Nothing():
      		 pass
      

Call Nothing function and assign return value to a variable

      		ret = Nothing()
      		type(ret)
      		<class 'NoneType'>
      

Programatically you can check return type using is operator

		>>> ret is None
		True
	

Let's modify Nothing Function, add return statement after pass, and then add print statement.

	>>> def Nothing():
		  pass
		  return
		  print("After return")

       	>>>Nothing()
       

pass is nothing but a null statement. return statement after pass, will return control back to the caller. so that finished execution of function Nothing(). What about print statement after return statement, control already passed back to the caller,it becomes unreachable code. Function never execute print statement

Python function can return List,Set,Dictionary,String etc.,

Following function mylist takes one object, that should be a sequence. "Alphabets" string object supports iteration,so it can be passed to list constructor

		def mylist(obj):
		   return list(obj)
		   
		#Calling above function

		newList = mylist("Alphabets")
				
		type(newList)
		<class 'list'>

		print(newList)
		['A', 'l', 'p', 'h', 'a', 'b', 'e', 't', 's']
	

Let's Add Exception Handling to above function. obj argument is iteratable, list with object values returned. if obj is not iteratable(int, float) values, function returns empty list , as shown below.

		def mylist(obj):
		   try:
   		     return list(obj)
		   except Exception as e:
		     return list()
		     
		newList = mylist("Alphabets")
		print(newList)
		['A', 'l', 'p', 'h', 'a', 'b', 'e', 't', 's']

		newList = mylist(123)
		print(newList)
		[]				     
	

Let's write Another Function which returns Dictionary Data type. Dictionary maintains key value pair, In this example collecting personal details key is a string object, value can be any type.

def getDetails():
                return {'Name':'Sam',
                        'Age':34,
                        'DOB':1973,
                        'hasJob':False,
                        'Monthly_Income':20000
                }

d=getDetails()
print(type(d))
print(d)

#OUTPUT
<class 'dict'>
{'Name': 'Sam', 'Age': 34, 'DOB': 1973, 'hasJob': False, 'Monthly_Income': 20000}

Programatically user can check whether variable 'd' is dictionary object or not. isinstance(d, dict) returns boolean value True

In Python return type checked the value it returned, you cannot specify return type explicitely.

		import random
		
		def pickup():
		  return random.choice([1,   2, 3.33333,  4.55555, 10.999,'jhon peter'])
	

Everytime you call , it returns different Datatype value. because it is a random choice function, list has all types of data i.e int,float and string, randomly picking one element at a time.

>>> pickup()
1
>>> pickup()
3.33333
>>> pickup()
1
>>> pickup()
'jhon peter'
>>> pickup()
2
>>> pickup()
1
>>> pickup()
1
>>> pickup()
10.999
>>> pickup()
10.999
>>> pickup()
10.999
>>> pickup()
4.55555
>>>