Marambo - 1 year ago 171

Python Question

I send you a question because I have a problem on python and I don't understand why.

I created a function "mut1" to change the number inside a list (with a probability to 1/2) either in adding 1 or subtracting 1, except for 0 and 9:

`def mut1 (m):`

i=np.random.randint(1,3)

j=np.random.randint(1,3)

if i==1:

if 0<m<9:

if j==1:

m=m+1

elif j==2:

m=m-1

elif m==0:

if j==1:

m=1

if j==2:

m=9

elif m==9:

if j==1:

m=0

if j==2:

m=8

print m

mut1 function well, for example, if I create a list P1:

`>>>p1=np.array(range(8),int).reshape((4, 2))`

After that, I apply "mut1" at a number (here 3) in the list p1

`>>>mut1(p1[1,1])`

Hovewer if I write:

`>>> p1[1,1]=mut1(p1[1,1])`

I have a message error:

Traceback (most recent call last): File "<stdin>", line 1, in

<module> TypeError: long() argument must be a string or a number, not

'NoneType'

Answer Source

That happens because you have to make your `mut1`

return an `numpy.int64`

type of result. So I tried with the following modified code of yours and worked.

```
>>> import numpy as np
>>> import random
>>>
>>> def mut1 (m):
... i=np.random.randint(1,3)
... j=np.random.randint(1,3)
... if i==1:
... if 0<m<9:
... if j==1:
... m=m+1
... elif j==2:
... m=m-1
... elif m==0:
... if j==1:
... m=1
... if j==2:
... m=9
... elif m==9:
... if j==1:
... m=0
... if j==2:
... m=8
... return np.int64(m)
...
>>> p1=np.array(range(8),int).reshape((4, 2))
>>> mut1(p1[1,1])
2
>>> p1[1,1]=mut1(p1[1,1])
>>>
```

So the only thing you need to change is to replace `print m`

with `return np.int64(m)`

and then should work!

You will easily understand why this happened with the following kind of debugging code:

```
>>> type(p1[1,1])
<type 'numpy.int64'>
>>> type(mut1(p1[1,1]))
<type 'NoneType'>
```