Python: How to store for loop result in a list?

Question

I have my output as below which is the result of iteration over looping. Basically the code below is to compare arrays of different sizes using intersection and union calculation.:

import numpy as py
import itertools
from itertools import izip
def diffs(a,b):
# collect sliding window differences
# length of window determined by the shorter array
# if a,b are not arrays, need to replace b[...]-a with
# a list comprehension
    n,m=len(a),len(b)
    if n>m:
    # ensure s is the shorter
        b,a=a,b # switch
        n,m=len(a),len(b)
    # may need to correct for sign switch
    result=[]
    for i in range(0,1+m-n):
        result.append(b[i:i+n]-a)
    return result

###################################################################

def alldiffs(a,b):
# collect all the differences for elements of a and b
# a,b could be lists or arrays of arrays, or 2d arrays
    result=[]
    for aa in a:
        for bb in b:
            result.append(diffs(aa,bb))
    return result

###################################################################

def count_total(a,b):
#count the total number of element for two arrays in different list
#return [sum(map(len, i)) for i in product(a, b)]
    y= lambda x:len(x)
    result=[]
    for a1 in a:
        for b1 in b:
            result.append(y(a1) + y(b1))
    return result

##################################################################

def count_zero(obj):
#count the total number of zero for two arrays in different list
    if isinstance(obj,list):
        return list(map(count_zero,obj))
    else:
        return Counter(obj)[0]

a=[np.array([2,2,1,2]),np.array([1,3])]
b=[np.array([4,2,1])]
c=[np.array([1,2]),np.array([4,3])]

for i,j in itertools.combinations([a,b,c],2):
    all_diffs=alldiffs(i,j)
    total=count_total(i,j)
    zero=count_zero(all_diffs)
    total=np.array(total)
    union=map(sub,total,zero)
    zero=np.array(zero).tolist()
    union=np.array(union).tolist()
    union=[list(x) for x in union]  
    sim=[[float(aaa) / bbb for (aaa, bbb) in itertools.izip(aa, bb)] \
        for (aa, bb) in itertools.izip(zero, union)]
    sim_comb=sum(sim,[])
    sum_of_sim=sum(sim_comb)
    number_sum=len(sim_comb)
    ave=sum_of_sim/number_sum
    one_ave=1-ave
    print one_ave

Output

>>> 
0.9
0.829166666667
0.875

How can I save them into list so my output will be like:

>>>
[0.9,0.829166666667,0.875]

Can anyone help me?

Can you show the loop that is producing those results? You can either use `list.append()` or a list comprehension. — Cory Kramer, Jun 09 '15 at 15:12
It return this error when i tried list.append(). TypeError: descriptor 'append' requires a 'list' object but received a 'float' — Xiong89, Jun 09 '15 at 15:15
For the second time, please show us the loop. We cannot help you by guessing alone — Cory Kramer, Jun 09 '15 at 15:15

score 1 · Accepted Answer · answered Jun 09 '15 at 15:32

Well the loop seems to be this one (at the end of the code):

for i,j in itertools.combinations([a,b,c],2):
    all_diffs=alldiffs(i,j)
    total=count_total(i,j)
    zero=count_zero(all_diffs)
    total=np.array(total)
    union=map(sub,total,zero)
    zero=np.array(zero).tolist()
    union=np.array(union).tolist()
    union=[list(x) for x in union]  
    sim=[[float(aaa) / bbb for (aaa, bbb) in itertools.izip(aa, bb)] \
        for (aa, bb) in itertools.izip(zero, union)]
    sim_comb=sum(sim,[])
    sum_of_sim=sum(sim_comb)
    number_sum=len(sim_comb)
    ave=sum_of_sim/number_sum
    one_ave=1-ave
    print one_ave

One possible solution would be to write:

output = []

for i,j in itertools.combinations([a,b,c],2):
    all_diffs=alldiffs(i,j)
    total=count_total(i,j)
    zero=count_zero(all_diffs)
    total=np.array(total)
    union=map(sub,total,zero)
    zero=np.array(zero).tolist()
    union=np.array(union).tolist()
    union=[list(x) for x in union]  
    sim=[[float(aaa) / bbb for (aaa, bbb) in itertools.izip(aa, bb)] \
        for (aa, bb) in itertools.izip(zero, union)]
    sim_comb=sum(sim,[])
    sum_of_sim=sum(sim_comb)
    number_sum=len(sim_comb)
    ave=sum_of_sim/number_sum
    one_ave=1-ave
    output += [one_ave]

print output

The two last lines could be: output.append(one_ave) print output — zezollo, Jun 09 '15 at 15:34

Leb · Answer 2 · 2015-06-09T16:32:31.243

0

As your comment suggested you need to convert them to a list items instead of floats.

sim=[[float(aaa) / bbb for (aaa, bbb) in itertools.izip(aa, bb)] \ 
    for (aa, bb) in itertools.izip(zero, union)]

In this line of code you're explicitly defining the values as float in here. Alternatively you can use use the map() function and split() the sim variable.

edited Jun 09 '15 at 16:32

answered Jun 09 '15 at 15:26

Leb

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TypeError: 'float' object is not iterable. I received this error because i can't put it in this way where list(one_ave) – Xiong89 Jun 09 '15 at 15:30
Thanks for reply. It's really helpful. – Xiong89 Jun 09 '15 at 15:39

Python: How to store for loop result in a list?

2 Answers2