# error with random.sample: raise NotImplementedError(“ >= and <= don't work with 0.”) NotImplementedError: >= and <= don't work with 0

138
June 26, 2018, at 7:30 PM

I have a problem with this code, I really dont understand why it cannot reach the second cycle of the most internal for:

``````def remove_random_links(A,E):
rs = random.sample(A.edges, E)
A.remove_edges_from(rs)
N = 30
L = [0,60,30,40,30,30,20,40]
rep = 15
d = []
g = []
for j in range(rep):
R = nx.grid_graph(dim=[N,N])
_deg = []
_gap = []
for i in L:
L = nx.laplacian_matrix(R)
eigwd, eigv = LA.eigh(L.todense())
eigw = np.sort(eigwd)
eigw0 = eigw[0]
eigw1 = eigw[1]
eigw2 = eigw[2]
eigw3 = eigw[3]
gap = eigw2 - eigw1
deg = eigw3 - eigw2
_deg.append(deg)
_gap.append(gap)
print("meow")
d.append(_deg)
g.append(_gap)
print("M")
mean_deg = [np.mean(d[i]) for i in range(rep)]
mean_gap = [np.mean(g[i]) for i in range(rep)]
std_deg = [np.std(d[i]) for i in range(rep)]
std_gap = [np.std(g[i]) for i in range(rep)]
``````

It goes on its first for cycle (the one in j) and then into its first for cycle in i, it completes it and then it is not able to do the second one because of this error with the function remove_random_links(), which gives me the following error:

File "/Users/Sofia/Desktop/delta.py", line 23, in remove_random_links(R,i)

File "/Users/Sofia/Desktop/delta.py", line 9, in remove_random_links rs = random.sample(A.edges, E)

File "/anaconda3/lib/python3.6/random.py", line 317, in sample if not 0 <= k <= n:

File "/anaconda3/lib/python3.6/site-packages/scipy/sparse/compressed.py", line 322, in ge "Comparing a sparse matrix with a scalar "

File "/anaconda3/lib/python3.6/site-packages/scipy/sparse/compressed.py", line 272, in _inequality raise NotImplementedError(" >= and <= don't work with 0.")

NotImplementedError: >= and <= don't work with 0.

It's because you are using the same variable `L` twice, once here

``````L = [0,60,30,40,30,30,20,40]
``````

Then reassigning it while iterating over it here

``````for i in L:
L = nx.laplacian_matrix(R)   #<--------change variable name
``````

Use different variable names and that should do the trick, try this for instance

``````import random
from numpy import linalg as LA
print A.edges, E
rs = random.sample(A.edges, E)
A.remove_edges_from(rs)
N = 30
L_edges = [0,60,30,40,30,30,20,40]    #<--- changed it to L_edges
rep = 15
d = []
g = []
for j in range(rep):
R = nx.grid_graph(dim=[N,N])
_deg = []
_gap = []
for i in L_edges:     #<--- changed it to L_edges
L = nx.laplacian_matrix(R)
eigwd, eigv = LA.eigh(L.todense())
eigw = np.sort(eigwd)
eigw0 = eigw[0]
eigw1 = eigw[1]
eigw2 = eigw[2]
eigw3 = eigw[3]
gap = eigw2 - eigw1
deg = eigw3 - eigw2
_deg.append(deg)
_gap.append(gap)
print("meow")
d.append(_deg)
g.append(_gap)
print("M")
mean_deg = [np.mean(d[i]) for i in range(rep)]
mean_gap = [np.mean(g[i]) for i in range(rep)]
std_deg = [np.std(d[i]) for i in range(rep)]
std_gap = [np.std(g[i]) for i in range(rep)]
``````
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