Tagged Questions
1
vote
1answer
33 views
Single Byte Multiplication in Python?
I have a requirement to decode a file using simple byte multiplication
For every byte in the file, the byte value is muliplied by 0x69. The result cannot be a word, it must be a single byte.
...
1
vote
2answers
53 views
Elementwise multiplication of several arrays in Python Numpy
Coding some Quantum Mechanics routines, I have discovered a curious behavior of Python's NumPy. When I use NumPy's multiply with more than two arrays, I get faulty results. In the code below, i have ...
0
votes
1answer
133 views
Karatsuba algorithm incorrect result
I just simply followed the pseudo code on wiki http://en.wikipedia.org/wiki/Karatsuba_algorithm
But the result of this implementation is very unstable.
It works sometimes but in case like 100*100. It ...
0
votes
2answers
84 views
Simple Multiplication of two fields in OpenErp
I have two fields in a class, in a third field i need the multiplication result of the two fields declared before.
For example:
_columns = {
'Item' : fields.integer('Items'),
...
1
vote
1answer
100 views
A function that takes two matrices as input, and returns a matrix with A * B. In Python
I am trying to figure out how to create a dot product matrix. Here is the code I have made so far:
C = [[4,1,9], [6,2,8], [7,3,5]]
D = [[2,9], [5,2], [1,0]]
def prettyPrint(A):
for i in ...
1
vote
4answers
66 views
How to multiply each row in a matrix by each column in the second matrix in Python?
I know the steps to multiply two matrices are as follow
Step 1: Make sure that the the number of columns in the 1st one equals the number of rows in the 2nd one.
Step 2: Multiply the elements of ...
6
votes
3answers
2k views
Python: multiply all items in a list together
I have a problem. I need to write a function, that takes
a list of numbers and multiply them together. example:
[1,2,3,4,5,6] will give me 1*2*3*4*5*6. I could really use your help.
0
votes
1answer
165 views
Matrix multiplication in Python
Hello (excuse my English), I have a big doubt in python with matrix multiplication, I create a list of lists and multiplied by a scaling matrix, this is what I've done and I can not alparecer perform ...
3
votes
5answers
103 views
Multiply Adjacent Elements
I have a tuple of integers such as (1, 2, 3, 4, 5) and I want to produce the tuple (1*2, 2*3, 3*4, 4*5) by multiplying adjacent elements. Is it possible to do this with a one-liner?
-2
votes
3answers
311 views
How do I multiple all integers in a list? --Python
list1= [1,2,3,4]
1) I want to multiply every element in this list in order to output 24. How do I do this in python without using a for loop? Are there in-built libraries to do this?
2) And what ...
0
votes
1answer
374 views
Strassen Matrix Multiplication — close, but still with bugs
I'm trying to implement Strassen Matrix multiplication in Python. I've got it working somewhat. Here's my code:
a = [[1,1,1,1],[2,2,2,2],[3,3,3,3],[4,4,4,4]]
b = ...
1
vote
7answers
266 views
multiplication game python
I am supposed to write a program in python that asks the user how many multiplication questions they want, and it randomly gives them questions with values from 1 to 10. Then it spits out the ...
1
vote
1answer
188 views
Multiplying two polynomials mod n,x^r-1 using long integers: what is the correct window size?
Using a window multiplication algorithm to multiply two polynomials[coefficients in Z/nZ and the whole polynomial mod x^r-1 for some r] using long-integer multiplications, what size should I give to ...
1
vote
3answers
211 views
Python and Powers Math
I've been learning Python but I'm a little confused. Online instructors tell me to use the operator ** as opposed to ^ when I'm trying to raise to a certain number. Example:
print 8^3
Gives an ...
-2
votes
3answers
114 views
Multiply matrix by list in Python
I am looking for a way to achieve the following in Python and can't figure out how to do it:
a=[[0,1],[1,0],[1,1]]
b=[1,0,5]
c=hocuspocus(a,b)
--> c=[[0,1],[0,0],[5,5]]
So basically I would ...
7
votes
2answers
487 views
Elementwise multiplication of arrays of different shapes in python
Say I have two arrays a and b,
a.shape = (5,2,3)
b.shape = (2,3)
then c = a * b will give me an array c of shape (5,2,3) with c[i,j,k] = a[i,j,k]*b[j,k].
Now the situation is,
a.shape = ...
1
vote
1answer
1k views
Vector Matrix multiplication in python?
So I'm trying to multiply a matrix by a vector. And python keeps on throwing up an error. Here is the code that I'm trying:
def matmult(m, v):
rows = len(m)
w = [0]*rows
irange = ...
1
vote
2answers
426 views
Karatsuba algorithm in Python
So I am implementing Karatsuba's multiplication algorithm in python. Right now I have infinite recursion and cannot figure it out. Any ideas? I will provide more code if needed.
def multiply(self, ...
3
votes
2answers
632 views
Elementwise multiply 1D-numpy arrays (shapes (k,1) or (k,)) and have result have the shape of the first
I would like to implement a diagonal matrix apply function that is created by providing the diagonal d first, and then doing a bunch of matrix-vector multiplications with x. Of course I wouldn't want ...
0
votes
1answer
172 views
Python: division and multiplication of timedelta64 type with floats
I am having difficulties multiplying the numpy datatype timedelta64 with floats.
For a task i need to calculate the period of a star using Kepler's second law. There are a lot of data points, so I ...
1
vote
4answers
796 views
Python Multiplying Integers inside “print()”
So I have the code (Relevant code):
print("You have chosen to bet on the even numbers")
valin = input("How much would you like to bet?: ")
print("If it lands on an even number, you win", valin*2)
...
0
votes
5answers
349 views
Why do I get an error when I call int(input()) where input is decimal (eg. '87.94')?
I'm a programming newbie having difficulty with Python multiplication. I have code like this:
def getPriceDiscount():
price = int(input())
if price > 3000:
priceDiscount = price * ...
0
votes
1answer
122 views
Prevent overflow errors when multiplying and powering in Python
How would you prevent the errors when calling function biased_random defined below and what are the limits for arguments scale and bias to hold for preventing problems with big or small numbers?
def ...
0
votes
1answer
291 views
Lattice Multiplication with threads, is it more efficient?
which one is faster:
Using Lattice Multiplication with threads(big numbers) OR
Using common Multiplication with threads(big numbers)
Do you know any source code, to test them?
...
7
votes
4answers
995 views
Karatsuba algorithm too much recursion
I am trying to implement the Karatsuba multiplication algorithm in c++ but right now I am just trying to get it to work in python.
Here is my code:
def mult(x, y, b, m):
if max(x, y) < b:
...
9
votes
4answers
2k views
Python list multiplication: [[…]]*3 makes 3 lists which mirror each other when modified
Why this is happening? I don't really understand:
>>> P = [ [()]*3 ]*3
>>> P
[[(), (), ()], [(), (), ()], [(), (), ()]]
>>> P[0][0]=1
>>> P
[[1, (), ()], [1, (), ...
1
vote
7answers
1k views
Having trouble with multiplying a variable with a number
I'm trying to shorten my code and have more functionality but its not working right.
Heres my code(basically)
def times4():
number = droid.dialogGetInput('Input', 'Enter a number between 1 and ...
3
votes
2answers
578 views
Deepcopy on nested referenced lists created by list multiplication does not work
As much as I love Python, the reference and deepcopy stuff sometimes freaks me out.
Why does deepcopy not work here:
>>> import copy
>>> a = 2*[2*[0]]
>>> a
[[0, 0], [0, ...
2
votes
3answers
214 views
Python basic maths
My friend wrote up this script for me to calculate the quantity of construction materials needed for a theoretical site.
It basically takes 2 numbers and increases them independently until the large ...
4
votes
4answers
4k views
Python long multiplication
I'm in need of an algorithm faster than the current normal python long multiplication ,
I tried to find a decent karatsuba implementation , but I can't.
def main():
a=long(raw_input())
...
