In this Tutorial, we will be discussing the difference between Python 2 and Python 3, so here we have some differences between Python 2.0 and 3.0.

In this Tutorial, I would be covering following topics :

1. Expression
2. Print option
3. Not equal operator.
4. Range.
5. Automated Python 2to3py.
6. Performance.
7. Some of major Housekeeping changes.
8. Having Problems.

So here X is a version just like 2.1 2.2 2.7 and in Python 3 point X which is Python 3.1 to 3.5 3.6 so now

let's see the differences Python 2 and Python 3

1 Expression :

Expressions represent something, like a number, a string, or an instance of a class. Any value is an expression ! Anything that does something is a statement. Any assignment to a variable or function call is a statement. Any value contained in that statement in an expression.

To Get expression In python 2 :

here what is evaluated expression.

Suppose we have a input in python 2 which is raw input after that some value.

X = raw_input ("enter some values")

To Get evaluated expression In python 3 :

But python 3 we have a input after that some values.

X = input ("enter some values")

Here So whatever we enter then value is assigned variable x, in both python 2 and python 3. So when i enter 2*6 in Python 2 result will be 12, which means you will get evaluated values.

But in Python 3 when run this program 2*6 then we get that result is string values which is like “2*6” in string format.

Then how will get the evaluated value in Python 3, so get evaluated resulted we have to use a expression or we can say function which is eval, when you write eval before the input so it will turn a evaluated value in Python.

Ex:

 x= eval(input("enter some values")) = 12 

Detailed Expression Examples of Python 2 and Python 3 :

In python 2 :

Input :

name = input("What is your name? ")
print ("Hello, %s." %name)

Output :

In python 3 :

Input :

name = input("What is your name? ")
print ("Hello, %s." %name)

Output :

So this is main difference in Python 2 and Python 3, which is evaluated expression.

2 Print option

In Python 2 print is statement where as Python 3 print is a function, in Python 2 we don't need to add parenthesis but in Python 3 we need the write the values in parenthesis.

Ex :

Python 2 - print "hello world"
Python 3 - ("hello world")

Python 2

Input :

print "hello world"

Output :

Python 3 :

Input :

1 != 1.0
print (False)

Output :

3 Not equal operator

let's move to the third difference, when we use a not equal to operator in python 2 so for that we have to use or greater than and less than sign.

But in Python 3 there is a general operator which is exclamation marks and equal to , so this operator is used in other languages that's why I call a general operator.

Ex :

Python 2 - <> operator is used for not equal
Python 3 - ! operator is used for not equal

In python 2 :

Input :

1 <> 1.0
print "False"

Output :

In Python 3 :

Input :

1 != 1.0
print (False)1 != 1.0
print (False)

Output :

4 Range

let's move to the fourth difference which is range in Python 2 and Python 3.

so what is the range?

Range is used in for loop iterate the values which is a integer. so when we use a range in Python programing to the it will return a list.

so here you can see X equal to Range 10 and when we check the variable X it returned our list type, which means that in Python 2 range is the type of list. when I write X and after that we get a list of object. which is 0 1 2 3 4 5 6 7 8 9.

so now let's move to the Python 3 when we write x equal to range 5

So this value of range 5 is assigned to the variable X and when we check the type for variable X then it returned a range object itself which means that in Python 3 range is a range object itself, so these are the key difference between Python 2 and Python 3.

Detailed Range Examples of Python 2 and Python 3 :

Python 2 :

Input

print range(0,10,1)

Output

Python 3

Input

 print(list(range(10)))

Output

5 Automated Python 2to3py. :

Now let's move to the topic which is how to automate the Python 2 script into Python 3 code.

Here we can Test with simple program like Add 2 Numbers in python.

Python 2 :

Input

n1 = 1
n2 = 2
add = float(n1) + float(n2)
print 'sum of {0} and {1} is {2}'.format(n1, n2, add)

Output

Now Using 2 to 3 Translation We can convert the above Code

Input :

n1 = 1
n2 = 2
add = float(n1) + float(n2)
print('sum of {0} and {1} is {2}'.format(n1, n2, add))

Output :

So here we see it can be converted to Python 3 x code by 2 to 3 on the command line, so this is the way to convert a Python 2 program into Python 3 so that is all about the difference between the Python 2 and the Python 3.

• Python provides its own tool called 2to3.py. Which runs a bunch of scripts to translate your python 2 code into 3.
• Not perfect, but it does an amazing job.
• After converting, go in an manually fix up the problems.

6 Performance :

In Python 3 most of the performance issues have been fixed are almost negligible when comparing current python 3 to python 2 benchmarks.

7 Some of major Housekeeping changes :

Python - 2

• print functional brackets optional.
• Prefix string with u to make unicode string.
• Division of integers always return integer - 5/2=2.
• Raw_input () reads string.
• input() evaluates data read.
• generator .next().

Python - 3

• print functional brackets compulsory.
• String unicode by default.
• Division of integers may result in float - 5/2=2.5.
• Raw_input() not available.
• Input always reads string.
• Next (generator).
• Py2 to py3 utility.
• Dictionary .keys() and .values() returns a view not a list.
• Can no longer use comparison operators on non natural comparisons.

Eg. None < None will raise a TypeError instead of returning false.

• Percent (%) string formatting operator is deprecated use the .format() Function or concatenation.

8 Having Problems :

• You may encounter an error here and there if you have been working in python 2.x for some time.
• Just google the problem, it's almost certain that someone has had that problem too when moving to python3

I hope you have enjoyed reading this Python Tutorial. We have covered all the basics Difference in Python 2 and Python 3, so you can start practicing now. Happy Learning