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Xrange In Python 3.6 | Introduction To Python 3 Xrange

Python Tutorial - range vs xrange function

NameError: name ‘xrange’ is not defined

In Python 2, the xrange function lets you create a range of numbers. Consider the following code snippet:

print(xrange(0, 3))

Our code returns [0, 1, 2], which is all the numbers in the range of 0 and 3 (exclusive of 3). The

xrange()

function returns a list of numbers.

Python 3 removed the

xrange()

function in favor of a new function called range(). The

range()

function, like

xrange()

, produces a range of numbers.

There are two differences between

xrange()

and

range()

;


  • xrange()

    and

    range()

    have different names.
  • The

    xrange()

    function generates a list of numbers. The

    range()

    function generates an object.

Because the

range()

function generates an object, you have to convert it into a list if you want to view a list of numbers. Otherwise, these two methods function in the same way.

Python3


import


sys


range


10000


xrange


10000


print


"The size allotted using range() is : "


print


(sys.getsizeof(a))


print


"The size allotted using xrange() is : "


print


(sys.getsizeof(x))

Output:

The size allotted using range() is : 80064The size allotted using xrange() is : 40

Operations Usage of xrange() and range() Function

A range() returns the list, all the operations that can be applied on the list can be used on it. On the other hand, as xrange() returns the xrange object, operations associated with the list cannot be applied to them, hence a disadvantage.

Python Tutorial - range vs xrange function
Python Tutorial – range vs xrange function

The Solution

We’ve used the

xrange()

function to generate a range of numbers. In Python 2, this would be valid. We are using Python 3 to run our program, which means we cannot reference the

xrange()

function.

To solve our error, we need to replace

xrange()

with the

range()

method:

for l in range(0, to_view): print(l + 1, leaderboard[l])

For this use case, both

xrange()

and

range()

will return the same result. Let’s run our code to see if it works:

How many scores would you like to view? 2 1 Alex 2 Jonas

Our program successfully displays the names of the players in the tournament who appear in the first two positions on the leaderboard.

An Example Scenario

We’re going to write a program that displays the first few players who are at the top of a card game leaderboard. To start, let’s declare our leaderboard as a list:

leaderboard = [“Alex”, “Jonas”, “Emma”, “Kate”]

Next, we’re going to ask the user how many scores they would like to view:

to_view = int(input(“How many scores would you like to view? “))

We convert the value that a user inserts into an integer. This is because the

xrange()

function only supports integers.

Next, let’s iterate over our leaderboard list using a for loop. We will only display the number of results that the user has requested to view on the console:

for l in xrange(0, to_view): print(l + 1, leaderboard[l])

We use the

xrange()

function to generate a range of numbers between 0 and the number the user inserted. In our for loop, we use a

print()

statement to print out the leaderboard entry that correlates with the number in the

xrange()

list that our loop is viewing.

We print out the value of “l” plus one alongside the name of a player. This lets us see their position. Because lists are indexed from zero, we add one to “l”. This prevents the first player on our list being at position “0” and so on.

Let’s run our code and see what happens:

How many scores would you like to view? 2 Traceback (most recent call last): File “main.py”, line 5, in

for l in xrange(0, to_view): NameError: name ‘xrange’ is not defined

Our program returns an error.

range vs xrange in Python 2 and Python 3
range vs xrange in Python 2 and Python 3

Introduction to Python 3 xrange

Python 3 xrange and range methods can be used to iterate a given number of times in for loops. There is no xrange in Python 3, although the range method operates similarly to xrange in Python 2. We should use range if we wish to develop code that runs on both Python 2 and Python 3. This function returns a generator object that can only be looped to display numbers.

What is Python 3 xrange?

  • The only specific range is displayed only when it is requested, leading to the term “lazy evaluation.”
  • If we are transitioning between Python 3 and Python 2, we could imagine that xrange objects in Python 2 and range objects in Python 3 are nearly identical. Isn’t it likely that they merely renamed xrange to range.
  • The xrange function is a little more constrained than the range function in Python 3.
  • When we ask for documentation for xrange using the help function, we get a list of dunder methods. When we employ several shared properties between different objects, Python uses Dunder methods like the len and str functions.
  • Xrange is a built-in function that generates integers or whole numbers within a specified range. If we are using both 3 and 2.x the range and xrange comparison be useful. It’s because 3.x’s range method is simply a reimplementation of 2.x’s xrange. It works in a similar fashion to the xrange.
  • Xrange returns a lazily evaluating sequence object. It is far more efficient, as it just computes the next value when it is required (through an xrange sequence object), rather than creating a list of all possible values as range does.
  • Range is similar to xrange and it returns a list. We will have to do if we need to generate the list.
  • Range replaces xrange, which is no longer available. We can’t use xrange to write Python 3 code.
  • The xrange type has the advantage of always using the same amount of memory, regardless range size will represents.
  • This function returns a generator object that can only be looped to display numbers. The xrange function works the same as the range function in generating a sequence of numbers. However, only Python 2.x uses xrange, while 3.x uses range.

How to Use Python 3 xrange?

1. While using the xrange function we need to specify the return type of function.

Code:


py = xrange(1,10000) print ("Xrange return type: ") print (type(py))

Output:

2. When compared to the variable storing the range created by xrange. Range returns a list, whereas xrange returns an xrange object.

Code:


import sys py = xrange(1,10000) print ("Allocates size by using xrange:") print (sys.getsizeof (py))

Output:

3. Range produces a list, it can be used with any operation that can be applied to a list. However, because xrange returns an xrange object, actions related to lists cannot be performed on it.

Code:


py = xrange(1,6) print ("List using xrange: ") print (py[2:5])

Output:

4. Xrange is faster to implement than range since it only evaluates the generator object holding the values required by lazy evaluation. The xrange function is deprecated in 3, we should use the range if we wish to develop code that will run on both 2 and 3. If we are iterating over the same sequence several times, the range is faster. Xrange must reconstruct the integer object each time it is called, whereas range will return genuine integer objects.

Functions

The syntax of the xrange function consists of 3 parameters:

Syntax:


xrange(start, end, step)

  • Start: This parameter indicates the sequence of numbers that should begin.
  • End: This parameter indicates the sequence of numbers will come to an end.
  • Step: This is the step parameter that was used in the function.

The end position must be defined. In the following example, we have defined the end parameter.

Code:


print ("End position\n") py_end = 7 print ("Position:", py_end) py = xrange(py_end) print(py) for py1 in py: print (py1)

Output:

In the below example we are defining the start, end, and step parameters with the function are as follows:

Code:


print("Start, End and Step parameter") py1 = 2 py2 = 5 py3 = 2 print ("start pos:", py1) print ("end pos:", py2) print ("step:", py3) py = xrange (5,13,2) print (py) for py4 in py: print (py4)

Output:

NameError

Xrange error message appears to imply that we are attempting to use 3 to execute a Python 2 codebase. In Python 2, the xrange method is frequently used to generate an iterable object, which behaves like a generator. The range function in Python 3 is similar to the method of xrange, hence there is no separate xrange method. As a result, using xrange in Python 3 will result in a NameError: name.

Below is the example of NameError as follows.

In the below example we are using “self” which was not defined so it will show this NameError message as the name “self is not defined.”

Code:


for py in xrange (self.epoch): py1 = py*b_size py2 = min((py+1)*b_size, d_size) self.rank.append (np.asarray (self.t_rank [py1:py2]))

Output:

Conclusion

Python 3 xrange and range methods can be used to iterate a given number of times in for loops. Range in Python 3 replaces xrange, which is no longer available. We can’t use xrange to write 3 code. Xrange returns a lazily evaluating sequence object.

Recommended Articles

This is a guide to Python 3 xrange. Here we discuss the introduction, how to use, function,s and name error respectively. You may also have a look at the following articles to learn more –

In Python 3, the xrange function was removed. If you try to use the xrange function in a Python 3 program, you’ll encounter the

NameError: name ‘xrange’ is not defined

error.

In this guide, we’re going to discuss what this error means and why you may encounter it. We’ll discuss an example of this error so you can learn how to fix it in your code.

3.6.3 XRange Type

The

xrange

type is an immutable sequence which
is commonly used for looping. The advantage of the

xrange

type is that an

xrange

object will always take the same amount
of memory, no matter the size of the range it represents. There are
no consistent performance advantages.

XRange objects have very little behavior: they only support indexing,
iteration, and the

len()

function.

See


About this document…


for information on suggesting changes.

Updated March 29, 2023

The difference between xrange vs. range functions in Python 2 and Python 3 (Tutorial)
The difference between xrange vs. range functions in Python 2 and Python 3 (Tutorial)

Python3


range


10000


xrange


10000


print


"The return type of range() is : "


print


type


(a))


print


"The return type of xrange() is : "


print


type


(x))

Output:

The return type of range() is :

The return type of xrange() is :

Speed of xrange() and range() Function

The variable storing the range created by range() takes more memory as compared to the variable storing the range using xrange(). The basic reason for this is the return type of range() is list and xrange() is xrange() object.

Python xrange() function

The xrange() function in Python is used to generate a sequence of numbers, similar to the Python range() function. The Python xrange() is used only in Python 2.x whereas the range() function in Python is used in Python 3.x.

Return Type in range() vs xrange()

This xrange() function returns the generator object that can be used to display numbers only by looping. The only particular range is displayed on demand and hence called “lazy evaluation“, whereas, in Python range() function returns a range object (a type of iterable).

Chapter 6- range() and xrange() in python #andytechshow #python #hindi #tutorial
Chapter 6- range() and xrange() in python #andytechshow #python #hindi #tutorial

Difference between range() and xrange() in Python

Because of the fact that xrange() evaluates only the generator object containing only the values that are required by lazy evaluation, therefore is faster in implementation than range().

Important Points:

  • If you want to write code that will run on both Python 2 and Python 3, use range() as the xrange function is deprecated in Python 3.
  • range() is faster if iterating over the same sequence multiple times.
  • xrange() has to reconstruct the integer object every time, but range() will have real integer objects. (It will always perform worse in terms of memory, however)
Returns a list of integers. Returns a generator object.
Execution speed is slower Execution speed is faster.
Takes more memory as it keeps the entire list of elements in memory. Takes less memory as it keeps only one element at a time in memory.
All arithmetic operations can be performed as it returns a list. Such operations cannot be performed on xrange().
In python 3, xrange() is not supported. In python 2, xrange() is used to iterate in for loops.

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Conclusion

The “NameError: name ‘xrange’ is not defined” error is raised when you try to use the

xrange()

method to create a range of numbers in Python 3. To solve this error, update your code to use the

range()

method that comes with Python 3.


range()

is the Python 3 replacement for

xrange()

. Now you have the know-how you need to solve this error like a pro!

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Flake8 testing of https://github.com/kentsyx/Neural-IMage-Assessment on Python 3.6.4

$ flake8 . –count –select=E901,E999,F821,F822,F823 –show-source –statistics

./model.py:40:14: F821 undefined name ‘xrange’
for i in xrange(1, length + 1):
^
./model.py:57:14: F821 undefined name ‘xrange’
for i in xrange(mini_batch_size):
^
2 F821 undefined name ‘xrange’
2

The text was updated successfully, but these errors were encountered:

@cclauss Yes I am aware, the code is written in Python 2.
You can add

from six.moves import xrange

in the import statements to make this error message disappear, or you can just replace xrange with range since in Python 3 range is implemented the same as xrange in Python 2.

xrange

range

Sorry, something went wrong.

No branches or pull requests

Learn Python – Python tutorial – python ranges – Python examples – Python programs

range() and xrange() are two functions that could be used to iterate a certain number of times in for loops in Python. In Python 3, there is no xrange , but the range function behaves like xrange in Python 2.If you want to write code that will run on both Python 2 and Python 3, you should use range().

range() – This returns a list of numbers created using range() function.xrange() – This function returns the generator object that can be used to display numbers only by looping. Only particular range is displayed on demand and hence called “lazy evaluation“.

Both are implemented in different ways and have different characteristics associated with them. The points of comparisons are:

  • Return Type
  • Memory
  • Operation Usage
  • Speed

range() returns – the list as return type.xrange() returns – xrange() object.

python – Sample – python code :


# Python code to demonstrate range() vs xrange() # on basis of return type # initializing a with range() a = range(1,10000) # initializing a with xrange() x = xrange(1,10000) # testing the type of a print ("The return type of range() is : ") print (type(a)) # testing the type of x print ("The return type of xrange() is : ") print (type(x))

python tutorial – Output :

The return type of range() is :

The return type of xrange() is :

The variable storing the range created by range() takes more memory as compared to variable storing the range using xrange(). The basic reason for this is the return type of range() is list and xrange() is xrange() object.

python – Sample – python code :


# Python code to demonstrate range() vs xrange() # on basis of memory import sys # initializing a with range() a = range(1,10000) # initializing a with xrange() x = xrange(1,10000) # testing the size of a # range() takes more memory print ("The size allotted using range() is : ") print (sys.getsizeof(a)) # testing the size of a # range() takes less memory print ("The size allotted using xrange() is : ") print (sys.getsizeof(x))

python tutorial – Output :

The size allotted using range() is : 80064 The size allotted using xrange() is : 40

As range() returns the list, all the operations that can be applied on the list can be used on it. On the other hand, as xrange() returns the xrange object, operations associated to list cannot be applied on them, hence a disadvantage.

python – Sample – python code :


# Python code to demonstrate range() vs xrange() # on basis of operations usage # initializing a with range() a = range(1,6) # initializing a with xrange() x = xrange(1,6) # testing usage of slice operation on range() # prints without error print ("The list after slicing using range is : ") print (a[2:5]) # testing usage of slice operation on xrange() # raises error print ("The list after slicing using xrange is : ") print (x[2:5])

Error:

Traceback (most recent call last): File “1f2d94c59aea6aed795b05a19e44474d.py”, line 18, in print (x[2:5]) TypeError: sequence index must be integer, not ‘slice’

python tutorial – Output :

The list after slicing using range is : [3, 4, 5] The list after slicing using xrange is :

Because of the fact that xrange() evaluates only the generator object containing only the values that are required by lazy evaluation, therefore is faster in implementation than range().

Important Points:

  • If you want to write code that will run on both Python 2 and Python 3, use range() as the xrange funtion is deprecated in Python 3
  • range() is faster if iterating over the same sequence multiple times.
  • xrange() has to reconstruct the integer object every time, but range() will have real integer objects. (It will always perform worse in terms of memory however)

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industry’, ‘Coding is behind almost everything that is powered by
electricity’, ‘Knowing how to code is a major requirement for
astronomers’, ‘The first computer didn’t use any electricity’, ‘Do you
know there is a coding language named “Go“’, ‘Computer programming is one
of the fastest-growing careers’, ‘Fortran (FORmula TRANslation) was the
name of the first programming language’, ‘The first programmer was the
daughter of a mad poet’, ‘Many programming languages share the same
structure’, ‘Coding will soon be as important as reading’, ‘How many
programmers does it take to change a light bulb? None, that’s a hardware
problem’, ‘Why do Java developers wear glasses? Because they can’t C’,
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pray’, ‘An engineer will not call it a bug — it’s an undocumented
feature’, ‘In a room full of top software designers, if two agree on the
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‘The best thing about a boolean is even if you are wrong, you are only off
by a bit’, ‘Linux is only free if your time has no value’, ‘The computer
was born to solve problems that did not exist before’,

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I think we use from six.moves import xrange elsewhere in the codebase to handle this incompatibility, without the potential for a performance regression on Python 2.7. Any file that uses xrange() should have this import at the top.

I think we use from six.moves import xrange elsewhere in the codebase to handle this incompatibility, without the potential for a performance regression on Python 2.7. Any file that uses xrange() should have this import at the top.

I think we use from six.moves import xrange elsewhere in the codebase to handle this incompatibility, without the potential for a performance regression on Python 2.7. Any file that uses xrange() should have this import at the top.

What is the difference between xrange and range in Python? Python Interview Questions
What is the difference between xrange and range in Python? Python Interview Questions

3.6.3 XRange Type

The

xrange

type is an immutable sequence which
is commonly used for looping. The advantage of the

xrange

type is that an

xrange

object will always take the same amount
of memory, no matter the size of the range it represents. There are
no consistent performance advantages.

XRange objects have very little behavior: they only support indexing,
iteration, and the

len()

function.

See


About this document…


for information on suggesting changes.

Redefining the xrange() Method

A potential solution to this problem is to define a variable called xrange at the start of your program that is equal to the

range()

function:

xrange = range

This is not a good solution to this error. This is because you are merely avoiding the problem of renaming existing methods. It would be confusing for someone to read through a Python 3 codebase and see

xrange()

statements, even if you have defined xrange as a variable.

The best solution is to rename your

xrange()

statements to

range()

and to make any necessary changes to ensure your codebase works in Python 3.

What is the difference between Xrange and range
What is the difference between Xrange and range

Some performance measurements, using

timeit

instead of trying to do it manually with

time

.

First, Apple 2.7.2 64-bit:


In [37]: %timeit collections.deque((x for x in xrange(10000000) if x%4 == 0), maxlen=0)
1 loops, best of 3: 1.05 s per loop

Now, python.org 3.3.0 64-bit:


In [83]: %timeit collections.deque((x for x in range(10000000) if x%4 == 0), maxlen=0)
1 loops, best of 3: 1.32 s per loop
In [84]: %timeit collections.deque((x for x in xrange(10000000) if x%4 == 0), maxlen=0)
1 loops, best of 3: 1.31 s per loop
In [85]: %timeit collections.deque((x for x in iter(range(10000000)) if x%4 == 0), maxlen=0)
1 loops, best of 3: 1.33 s per loop

Apparently, 3.x

range

really is a bit slower than 2.x

xrange

. And the OP’s

xrange

function has nothing to do with it. (Not surprising, as a one-time call to the

__iter__

slot isn’t likely to be visible among 10000000 calls to whatever happens in the loop, but someone brought it up as a possibility.)

But it’s only 30% slower. How did the OP get 2x as slow? Well, if I repeat the same tests with 32-bit Python, I get 1.58 vs. 3.12. So my guess is that this is yet another of those cases where 3.x has been optimized for 64-bit performance in ways that hurt 32-bit.

But does it really matter? Check this out, with 3.3.0 64-bit again:


In [86]: %timeit [x for x in range(10000000) if x%4 == 0]
1 loops, best of 3: 3.65 s per loop

So, building the

list

takes more than twice as long than the entire iteration.

And as for “consumes much more resources than Python 2.6+”, from my tests, it looks like a 3.x

range

is exactly the same size as a 2.x

xrange

—and, even if it were 10x as big, building the unnecessary list is still about 10000000x more of a problem than anything the range iteration could possibly do.

And what about an explicit

for

loop instead of the C loop inside

deque

?


In [87]: def consume(x):
....: for i in x:
....: pass
In [88]: %timeit consume(x for x in range(10000000) if x%4 == 0)
1 loops, best of 3: 1.85 s per loop

So, almost as much time wasted in the

for

statement as in the actual work of iterating the

range

.

If you’re worried about optimizing the iteration of a range object, you’re probably looking in the wrong place.

Meanwhile, you keep asking why

xrange

was removed, no matter how many times people tell you the same thing, but I’ll repeat it again: It was not removed: it was renamed to

range

, and the 2.x

range

is what was removed.

Here’s some proof that the 3.3

range

object is a direct descendant of the 2.x

xrange

object (and not of the 2.x

range

function): the source to 3.3

range

and 2.7

xrange

. You can even see the change history (linked to, I believe, the change that replaced the last instance of the string “xrange” anywhere in the file).

So, why is it slower?

Well, for one, they’ve added a lot of new features. For another, they’ve done all kinds of changes all over the place (especially inside iteration) that have minor side effects. And there’d been a lot of work to dramatically optimize various important cases, even if it sometimes slightly pessimizes less important cases. Add this all up, and I’m not surprised that iterating a

range

as fast as possible is now a bit slower. It’s one of those less-important cases that nobody would ever care enough to focus on. No one is likely to ever have a real-life use case where this performance difference is the hotspot in their code.

The range() and xrange() are two functions that could be used to iterate a certain number of times in for loops in Python. In Python3, there is no xrange, but the range function behaves like xrange in Python2. If you want to write code that will run on both Python2 and Python3, you should use range(). Both are implemented in different ways and have different characteristics associated with them. The points of comparison are:

  • Return Type
  • Memory
  • Operation Usage
  • Speed

Python3


range


xrange


print


"The list after slicing using range is : "


print


(a[


])


print


"The list after slicing using xrange is : "


print


(x[


])

Error:

Traceback (most recent call last): File “1f2d94c59aea6aed795b05a19e44474d.py”, line 18, in print (x[2:5])TypeError: sequence index must be integer, not ‘slice’

Output:

The list after slicing using range is : [3, 4, 5]The list after slicing using xrange is :

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