How to write fast into a file in python?
I need to write numbers into a file upto 50mb and it should be fast
can any one help me how to do that?
i had written the following code..
---
def create_file_numbers_old(filename, size):
start = time.clock()
value = 0
with open(filename, "w") as f:
while f.tell()< size:
f.write("{0}\n".format(value))
value += 1
end = time.clock()
print "time taken to write a file of size", size, " is ", (end -start),
"seconds \n"
--
it takes about 20sec i need 5 to 10 times less than that.
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Re: How to write fast into a file in python?
On Friday, May 17, 2013 8:50:26 AM UTC+5:30, lokesh...@gmail.com wrote:
> I need to write numbers into a file upto 50mb and it should be fast
>
> can any one help me how to do that?
>
> i had written the following code..
>
> ---
>
> def create_file_numbers_old(filename, size):
>
> start = time.clock()
>
>
>
> value = 0
>
> with open(filename, "w") as f:
>
> while f.tell()< size:
>
> f.write("{0}\n".format(value))
>
> value += 1
>
>
>
> end = time.clock()
>
>
>
> print "time taken to write a file of size", size, " is ", (end -start),
> "seconds \n"
>
> --
>
> it takes about 20sec i need 5 to 10 times less than that.
size = 50mb
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Scope of a class..help???
i had written the following code i am unable to create the instance of the class "Node" in the method "number_to_LinkedList" can any one help me how to do ?? and what is the error?? class Node: def __init__(self, value=None): self.value = value self.next = None def number_to_LinkedList(numbers): pass list_numbers = list(numbers) head_node = Node() #unable to create the instance saying UnboundedLocal head_node.value = list_numbers[0] head_node.next = None current_node = head_node for i in range(1,len(list_numbers)): new_node = Node() new_node.value = list_numbers[i] new_node.next = current_node current_node = new_node current_node.next = None while Node: print Node.data Node = Node.next -- http://mail.python.org/mailman/listinfo/python-list
2's Complement in python help.
Can anyone give me an idea of how to find the 2's Complement in python with an example -- http://mail.python.org/mailman/listinfo/python-list
Re: Scope of a class..help???
Thanks Chris Angelico, i am new to python can you suggest me how to remove the error and solve it. so,how can i create an instance for "Node" in that function??,is, it not possible to create an instance in such a way? -- http://mail.python.org/mailman/listinfo/python-list
Re: Scope of a class..help???
ok Peter Otten, but how to make a Class global?? -- http://mail.python.org/mailman/listinfo/python-list
help in obtaining binary equivalent of a decimal number in python
i need to get 32 bit binary equivalent of a decimal and need to change the 0's to 1's and 1's to 0's For Example if the input is 2 Output should be: the 32bit equivalent of 2 : 0010 and the 1's compliment is: 1101 is there any pre-defined function to get the above results in python?? -- http://mail.python.org/mailman/listinfo/python-list
help how to sort a list in order of 'n' in python without using inbuilt functions??
i need to write a code which can sort the list in order of 'n' without use builtin functions can anyone help me how to do? -- http://mail.python.org/mailman/listinfo/python-list
Re: help how to sort a list in order of 'n' in python without using inbuilt functions??
On Friday, May 24, 2013 1:34:51 PM UTC+5:30, lokesh...@gmail.com wrote: > i need to write a code which can sort the list in order of 'n' without use > builtin functions > > can anyone help me how to do? Note: the list only contains 0's,1's,2's need to sort them in order of 'n' -- http://mail.python.org/mailman/listinfo/python-list
Re: help how to sort a list in order of 'n' in python without using inbuilt functions??
On Saturday, May 25, 2013 10:54:01 AM UTC+5:30, Chris Angelico wrote: > On Sat, May 25, 2013 at 3:15 PM, wrote: > > > On Friday, May 24, 2013 1:34:51 PM UTC+5:30, lokesh...@gmail.com wrote: > > >> i need to write a code which can sort the list in order of 'n' without use > >> builtin functions > > >> > > >> can anyone help me how to do? > > > > > > Note: > > > the list only contains 0's,1's,2's > > > need to sort them in order of 'n' > > > > In that case, you're not really ordering them, you're counting them. > > Look at the collections module; you can very easily figure out how > > many of each there are, and then reconstruct the list afterward. > > > > ChrisA but i need to do it with out using builtin functions -- http://mail.python.org/mailman/listinfo/python-list
Re: help how to sort a list in order of 'n' in python without using inbuilt functions??
On Saturday, May 25, 2013 11:27:38 AM UTC+5:30, Steven D'Aprano wrote: > On Fri, 24 May 2013 22:39:06 -0700, lokeshkoppaka wrote: > > > > > On Saturday, May 25, 2013 10:54:01 AM UTC+5:30, Chris Angelico wrote: > > > > >> In that case, you're not really ordering them, you're counting them. > > >> Look at the collections module; you can very easily figure out how > > >> many of each there are, and then reconstruct the list afterward. > > > > > > but i need to do it with out using builtin functions > > > > > > How would you, an intelligent human being count them? > > > > Describe how you would count them in English, or whatever your native > > language is. > > > > "First I would start a tally for the number of zeroes, tally = 0. Then I > > look at each item in turn, and if it is 0, I add one to the tally. When I > > get to the end, I the number of zeroes is equal to the tally. > > > > Then I do the same for the number of ones, and the number of twos." > > > > Now turn that into Python code. > > > > tally = 0 > > for item in list_of_items: > > if item == 0: > > tally = tally + 1 > > > > print "The number of zeroes equals", tally > > > > > > > > -- > > Steven ya steven i had done the similar logic but thats not satisfying my professor he had given the following constrains 1. No in-built functions should be used 2. we are expecting a O(n) solution 3. Don't use count method -- http://mail.python.org/mailman/listinfo/python-list
help?? on functions
def shuffle(input, i, j): pass input = input[i:j+1] +input[0:i] + input[j+1:] def test_shuffle(): input = [1, 2, 3, 4, 5, 6] shuffle(input, 1, 2) assert [2, 3, 1, 4, 5, 6] == input i had done the above code but the problem is i had manipulated the "input" in function shuffle(input, i, j) but once i get back to the test_shuffle() function again the variable "input" does not reflect the changes made in shuffle(input, i, j) why ,please can any one describe why . and help how to reflect that change to the variable "input". -- http://mail.python.org/mailman/listinfo/python-list
Re: help?? on functions
On Monday, May 27, 2013 11:18:34 AM UTC+5:30, Steven D'Aprano wrote:
> On Sun, 26 May 2013 21:48:34 -0700, lokeshkoppaka wrote:
>
>
>
> > def shuffle(input, i, j):
>
> > pass
>
> > input = input[i:j+1] +input[0:i] + input[j+1:]
>
>
>
> "pass" does nothing. Take it out.
>
>
>
>
>
>
>
> > def test_shuffle():
>
> > input = [1, 2, 3, 4, 5, 6]
>
> > shuffle(input, 1, 2)
>
> > assert [2, 3, 1, 4, 5, 6] == input
>
> >
>
> >
>
> > i had done the above code but the problem is i had manipulated the
>
> > "input" in function shuffle(input, i, j) but once i get back to the
>
> > test_shuffle() function again the variable "input" does not reflect the
>
> > changes made in shuffle(input, i, j) why ,please can any one describe
>
> > why . and help how to reflect that change to the variable "input".
>
>
>
> The line of code:
>
>
>
> input = input[i:j+1] +input[0:i] + input[j+1:]
>
>
>
>
>
> takes the input list, makes three slices from that list, creates a new
>
> list, and then reassigns the LOCAL variable "input". This does not touch
>
> the variable on the outside of the function.
>
>
>
> This will be more clear if you use different names:
>
>
>
> # Outside the function.
>
> mylist = [1, 2, 3, 4, 5, 6]
>
> shuffle(mylist, 1, 2)
>
>
>
>
>
> Inside the function "shuffle", "input" is a local variable, and when you
>
> reassign to it, the variable "mylist" on the outside is not changed. Try
>
> this small function to see what I mean:
>
>
>
> def demo(input):
>
> print('local variable, before:', input)
>
> input = 100
>
> print('local variable, after:', input)
>
> print('non-local variable', mylist)
>
>
>
>
>
> mylist = [1, 2, 3, 4, 5, 6]
>
> demo(mylist)
>
>
>
>
>
>
>
> So, what can you do to fix this? You have two choices:
>
>
>
>
>
> 1) You can return the shuffled list. Add this line to the end of your
>
> shuffle function:
>
>
>
> return input
>
>
>
>
>
> and then inside the test function, do this:
>
>
>
> def test_shuffle():
>
> input = [1, 2, 3, 4, 5, 6]
>
> input = shuffle(input, 1, 2)
>
> assert [2, 3, 1, 4, 5, 6] == input
>
>
>
>
>
> 2) You can modify the input list in place.
>
>
>
> In this case, instead of reassigning the local variable "input" with the
>
> new list, you simply tell Python to stuff the new list inside the
>
> original list. You do that with a slice:
>
>
>
>
>
> input[:] = input[i:j+1] + input[0:i] + input[j+1:]
>
>
>
>
>
> That's a small difference from what you wrote, just three characters [:],
>
> but it makes a big difference in the effect. Instead of reassigning the
>
> local variable to the new list, it takes the existing list, and replaces
>
> each value inside it with the values taken from the new list. For example:
>
>
>
>
>
> py> mylist = [100, 200, 300, 400, 500, 600]
>
> py> mylist[3:5] = ['A', 'B', 'C']
>
> py> mylist
>
> [100, 200, 300, 'A', 'B', 'C', 600]
>
>
>
> py> mylist[1:] = [99, 98, 97]
>
> py> mylist
>
> [100, 99, 98, 97]
>
>
>
>
>
> Any questions?
>
>
>
>
>
> --
>
> Steven
Steven
wow, wonderful explanation ,i got it thanks a lot
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