Python error when calling NumPy from class method with map

Question

The following code throws me the error:

Traceback (most recent call last):
  File \"\", line 25, in 
    sol = anna.main()
  File \"\", line 17, in         


        

Answer 1

I'll try to add a precise answer to those that have already been given. numpy.sqrt has some limitations that math.sqrt doesn't have.

import math
import numpy  # version 1.13.3

print(math.sqrt(2 ** 64 - 1))
print(numpy.sqrt(2 ** 64 - 1))

print(math.sqrt(2 ** 64))
print(numpy.sqrt(2 ** 64))

returns (with Python 3.5) :

4294967296.0
4294967296.0
4294967296.0
Traceback (most recent call last):
  File "main.py", line 8, in 
    print(numpy.sqrt(2 ** 64))
AttributeError: 'int' object has no attribute 'sqrt'

In fact, 2 ** 64 is equal to 18,446,744,073,709,551,616 and, according to the standard of C data types (version C99), the long long unsigned integer type contains at least the range between 0 and 18,446,744,073,709,551,615 included.

The AttributeError occurs because numpy, seeing a type that it doesn't know how to handle (after conversion to C data type), defaults to calling the sqrt method on the object (but that doesn't exist). If we use floats instead of integers then everything will work using numpy:

import numpy  # version 1.13.3

print(numpy.sqrt(float(2 ** 64)))

returns:

4294967296.0

So instead of replacing numpy.sqrt by math.sqrt, you can alternatively replace calc = np.sqrt(food ** 5) by calc = np.sqrt(float(food ** 5)) in your code.

I hope this error will make more sense to you now.