CODEWITHSUNDEEP
pythonlistdivision
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Reputation: 2429

How to divide an integer by a list in Python?

sample = [['AAAA','BBBB','CCCC'],['BBBBB','FFFFF','GGGGG'],['AA','MM']]

I need to calculate 'a' such that a = summation 1/i; where i ranges from 1 to n-1. In the process, I need to divide an integer (MyInt) by a list.

i2 =[]
afinal =[]
for sub_list in sample:
    i1 = range(len(sample[0]))
    i1.pop(0)
    myInt = [1 for x in i1]
    newList = [float(int1)/float(x) for int1,x in zip(myInt,i1)]
    a = [sum(i) for i in zip(newList)]
afinal.append(a)
print afinal

However, I get the output as [[1.0]], whereas I should be getting an output with as [1.83333333333, 2.08333333333,1] numbers within a list.

Any idea where I may be going wrong?

Upvotes: 0

Views: 5507

Answers (3)

Right leg
Right leg

Reputation: 16700

If I understand well, you want to divide a by every element of your list. What you need is reduce:

l = [1, 2, 3, 4]
reduce((lambda x, y : x/y), l)

Will return the first element of l, which is 1, divided by all the other elements of l.

Explanation

reduce applies the first parameter to the first two elements of the second parameter, and repeats it with a new list whose first element is the result of the call, and the other elements are the elements of the passed list, started from the 3rd, until the second parameter has only one element.

Example call to clarify:

>>>reduce((lambda x, y : x+y), [1, 2, 3])
step 1: 1+2=3, so the new call is reduce((lambda x, y : x+y), [3, 3])
step 2: 3+3=6, so the new call is reduce((lambda x, y : x+y), [6])
step 3: [6] has only one element, so returns 6.

lambda x, y : x/y means "you know, that function that takes two arguments and that returns their quotient". This is an anonymous function.

Upvotes: 1

Mark Tolonen
Mark Tolonen

Reputation: 177481

I need to calculate 'a' such that a = summation 1/i; where i ranges from 1 to n-1

>>> n = 5
>>> a = sum(1.0 / i for i in range(1,n))
>>> a
2.083333333333333
>>> 1./1 + 1./2 + 1./3 + 1./4
2.083333333333333

Is that what you are trying to do?

Upvotes: 3

dvlper
dvlper

Reputation: 472

Assuming you are talking about (Integer division). I would prefer using Numpy. Following might be what you are looking for:

import numpy as np

a = np.array([1,2,3,4,5])     # a List
b = 3                         # INT Value
print b/a

Upvotes: 0

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