In Python, you can use the numpy library when working with arrays and certain math concepts like matrices and linear algebra.
But like every other aspect of learning and working with a programming language, errors are unavoidable.
In this article, you’ll learn how to fix the “TypeError: only size-1 arrays can be converted to Python scalars” error which mostly occurs when using the numpy library.
What Causes the TypeError: only size-1 arrays can be converted to Python scalars Error in Python?
The “TypeError: only size-1 arrays can be converted to Python scalars” error is raised when we pass in an array to a method that accepts only one parameter.
Here’s an example:
import numpy as np y = np.array([1, 2, 3, 4])
x = np.int(y) print(x) # TypeError: only size-1 arrays can be converted to Python scalars
The code above throws the “TypeError: only size-1 arrays can be converted to Python scalars” error because we passed the y array to the NumPy int() method. The method can only accept one parameter.
In the next section, you’ll see some solutions for this error.
How to Fix the TypeError: only size-1 arrays can be converted to Python scalars Error in Python
There are two general solutions for fixing the “TypeError: only size-1 arrays can be converted to Python scalars” error.
Solution #1 – Using the np.vectorize() Function
The np.vectorize() function can accept a sequence/an array as its parameter. When printed out, it returns an array.
Here’s an example:
import numpy as np vector = np.vectorize(np.int_)
y = np.array([2, 4, 6, 8])
x = vector(y) print(x)
# [2, 4, 6, 8]In the example above, we created a vector variable which will “vectorize” any parameter passed to it: np.vectorize(np.int_).
We then created an array and stored it in the y variable: np.array([2, 4, 6, 8]).
Using the vector variable we created initially, we passed the y array as a parameter: x = vector(y).
When printed out, we got the array — [2, 4, 6, 8].
Solution #2 – Using the map() Function
The map() function accepts two parameter in this case — the NumPy method and the array.
import numpy as np y = np.array([2, 4, 6, 8])
x = np.array(list(map(np.int_, y))) print(x)
# [2, 4, 6, 8]In the example above, we nested the map() function in a list() method so that we get the array retuned as a list and not a map object.
Solution #3 – Using the astype() Method
We can use the astype() method to convert a NumPy array to integers. This will prevent the “TypeError: only size-1 arrays can be converted to Python scalars” error from being raised.
Here’s how:
import numpy as np vector = np.vectorize(np.int_)
y = np.array([2, 4, 6, 8])
x = y.astype(int) print(x)
# [2 4 6 8]Summary
In this article, we talked about the “TypeError: only size-1 arrays can be converted to Python scalars” error in Python.
It is raised when we pass an array as a parameter to a numpy method that accepts only one parameter.
To fix the error, we used different methods like the np.vectorize() function, map() function, and astype() method.
Happy coding!