Change language

Important differences between Python 2.x and Python 3.x with examples

|

If we are porting our code or executing python 3.x code into python 2.x, it can be dangerous if integer division changes go unnoticed (since this does not cause any error). It is preferable to use a float (like 7.0 / 5 or 7 / 5.0) to get the expected result when we wrap our code.

print 7 / 5

print - 7 / 5  

 
"" "
Exit to Python 2.x
1
- 2
Output in Python 3.x:
1.4
- 1,4

 
# See Link below for details 
# https://python.engineering/division-operator-in-python/amp/
"" "

print function

This is the most famous change. This replaces the print function in Python 2.x with the print () function in Python 3.x, meaning that printing in Python 3.x requires an extra pair of parentheses.

print ’Hello, Geeks’   # Python 3.x does not support

print ( ’Hope You like these facts ’ )

  
"" "
Output in Python 2.x:
Hello geeks
Hope you like these facts

 
Output in Python 3.x:
File & quot; a.py & quot;, line 1

print Hello Geeks

^

SyntaxError: invalid syntax

 
Refer to the link below for details
https://python.engineering/g-fact- 25-print-single-multiple-variable-python / amp /
"" "

As we can see, if we use parentheses in Python 2.x, then this is not a problem, but if we don’t use parentheses in Python 3.x, we get SyntaxError.

Unicode:

In Python 2, the implicit type str — ASCII. But in Python 3.x the implicit type str is Unicode.

print ( type ( ’default string’ ))

print ( type (b ’string with b’ ))

 
"" "
Output in Python 2 .x (matches str in bytes)
"type & # 39; str & # 39;"
"type & # 39; str & # 39;"

 
Output in Python 3.x (bytes and str are different)
"class & # 39; str & # 39;"
"class & # 39; bytes & # 39;"
"" "

Python 2.x also supports Unicode

print ( type ( ’default string’ ))

print ( type (u ’string with b’ ))

 
"" "
Output in Python 2 .x (Unicode and str are different)
"type & # 39; str & # 39;"
"type & # 39; Unicode & # 39;"

 
Output in Python 3.x (Unicode and str are the same)
"class & # 39; str & # 39;"
"class & # 39; str & # 39;"
"" "

xrange:

xrange () in Python 2.x does not exist in Python 3.x. In Python 2.x, range returns a list, i.e. range (3) returns [0, 1, 2], and xrange returns an xrange object, that is, Xrange (3) returns an iterator object that works like a Java iterator and generates a number as needed. 
If we need to repeat the same sequence multiple times, we prefer range () because range provides a static list. xrange () rebuilds the sequence every time. xrange () does not support slices or other list methods. The advantage of xrange () is that it saves memory when the task is to iterate over a large range.

In Python 3.x, the range function now does what xrange does in Python 2.x, so, to keep our code portable, we could stick with using range instead. So, the range function in Python 3.x —  this xrange from Python 2.x.

for x in xrange ( 1 , 5 ):

print (x),

 

for x in range ( 1 , 5 ):

print (x),

  
" ""
Exit to Python 2.x
1 2 3 4 1 2 3 4

 
Exiting Python 3.x
NameError: name & # 39; xrange & # 39; undefined
"" "

Error handling:

Both versions there are small changes in error handling. In python 3.x, the "as" keyword is required.

try :

trying_to_check_error

except NameError, err:

  print err, ’ Error Caused’   # Will not work in Python 3.x

 
"" "
Output in Python 2.x:
name & # 39; ring_to_check_error & # 39; undefined Error caused

 
Output in Python 3.x:
File & quot; a.py & quot ;, line 3

except for NameError, err:

^

SyntaxError: invalid syntax
"" "

try :

  trying_to_check_error

except NameError as err: # & # 39; as & # 39; required in Python 3.x

print (err, ’Error Caused’ )

  
" ""
Output in Python 2.x:
(NameError ("name_update_check_error" is undefined "," An error was caused ")

  
Output in Python 3.x:
name & # 39; ring_to_check_error & # 39; undefined Error caused
"" "

_future_module:

This is basically not the difference between the two versions but it is useful to mention here. The idea of ​​the __future__ module — help in m games. We can use Python 3.x
If we plan to support Python 3.x in our 2.x code, we can use _future_, by importing it into our code.

For example, in the Python 2.x code below, we are using Python 3.x integer division behavior using the __future__ module

# In the following Python 2. x, separation works
# the same as Python 3.x because we are using __future__

from __ future__ import division

 

print 7 / 5

print - 7 / 5

Output:

 1.4 -1.4 

Another example where we use parentheses in Python 2.x using the __future__ module

from __ future__ import print_function 

 

print ( ’GeeksforGeeks’ )

Output:

 Python.Engineering 

Refer to this for more details on the __future __ module.

This st This article is provided by Arpit Agarwal . If you like Python.Engineering and would like to contribute, you can also write an article and mail it to [email protected] See your article appearing on the Python.Engineering homepage and help other geeks.

Please post comments if you find anything wrong or if you’d like to share more information on the topic under discussion

Shop

Learn programming in R: courses

$

Best Python online courses for 2022

$

Best laptop for Fortnite

$

Best laptop for Excel

$

Best laptop for Solidworks

$

Best laptop for Roblox

$

Best computer for crypto mining

$

Best laptop for Sims 4

$

Latest questions

NUMPYNUMPY

Common xlabel/ylabel for matplotlib subplots

12 answers

NUMPYNUMPY

How to specify multiple return types using type-hints

12 answers

NUMPYNUMPY

Why do I get "Pickle - EOFError: Ran out of input" reading an empty file?

12 answers

NUMPYNUMPY

Flake8: Ignore specific warning for entire file

12 answers

NUMPYNUMPY

glob exclude pattern

12 answers

NUMPYNUMPY

How to avoid HTTP error 429 (Too Many Requests) python

12 answers

NUMPYNUMPY

Python CSV error: line contains NULL byte

12 answers

NUMPYNUMPY

csv.Error: iterator should return strings, not bytes

12 answers

News


Wiki

Python | How to copy data from one Excel sheet to another

Common xlabel/ylabel for matplotlib subplots

Check if one list is a subset of another in Python

sin

How to specify multiple return types using type-hints

exp

Printing words vertically in Python

exp

Python Extract words from a given string

Cyclic redundancy check in Python

Finding mean, median, mode in Python without libraries

cos

Python add suffix / add prefix to strings in a list

Why do I get "Pickle - EOFError: Ran out of input" reading an empty file?

Python - Move item to the end of the list

Python - Print list vertically