Fixing RuntimeError: How to Solve Expected Scalar Type Long but Found Float in Python

In this guide, we will discuss the common RuntimeError that occurs in Python when the expected scalar type is a long integer but a float is found instead. We will delve into the root cause of this error, provide step-by-step solutions to fix it, and answer some frequently asked questions related to this issue.

Table of Contents

  1. Understanding the Error
  2. Step-by-Step Solutions
  3. Use the int() Function
  4. Use the round() Function
  5. Use the math.floor() Function
  6. Use the math.ceil() Function
  7. FAQs

Understanding the Error

The "Expected scalar type Long but found Float" error occurs in Python when a function or operation expects an integer input, but a floating-point number is provided instead. This is a common error when using libraries like PyTorch or NumPy, which rely on specific data types for their operations.

For example, if you are trying to create a tensor in PyTorch with floating-point data but specify the data type as a long integer, you will encounter this error.

import torch

data = [1.0, 2.0, 3.0]
tensor = torch.tensor(data, dtype=torch.long)

This code will raise the following error:

RuntimeError: Expected scalar type Long but found Float

Step-by-Step Solutions

There are several methods to resolve this error, depending on the desired outcome. Here are four possible solutions:

1. Use the int() Function

You can convert the floating-point number to an integer using the int() function. This method will truncate the decimal part of the float.

float_number = 3.14
integer_number = int(float_number)
print(integer_number)  # Output: 3

2. Use the round() Function

To round the floating-point number to the nearest integer, use the round() function.

float_number = 3.14
rounded_number = round(float_number)
print(rounded_number)  # Output: 3

3. Use the math.floor() Function

The math.floor() function rounds the floating-point number down to the nearest integer.

import math

float_number = 3.14
floored_number = math.floor(float_number)
print(floored_number)  # Output: 3

4. Use the math.ceil() Function

The math.ceil() function rounds the floating-point number up to the nearest integer.

import math

float_number = 3.14
ceiled_number = math.ceil(float_number)
print(ceiled_number)  # Output: 4


Q1: Can I fix this error by changing the data type in PyTorch?

Yes, you can change the data type of the tensor to torch.float or torch.double to match the data.

import torch

data = [1.0, 2.0, 3.0]
tensor = torch.tensor(data, dtype=torch.float)

Q2: How do I convert a list of floats to integers?

You can use a list comprehension with the int() function or any other desired rounding function.

float_list = [1.1, 2.2, 3.3]
integer_list = [int(x) for x in float_list]
print(integer_list)  # Output: [1, 2, 3]

Q3: How do I convert a NumPy array of floats to integers?

You can use the astype() method in NumPy to change the data type of an array.

import numpy as np

float_array = np.array([1.1, 2.2, 3.3])
integer_array = float_array.astype(int)
print(integer_array)  # Output: [1, 2, 3]

Q4: How do I convert a float to an integer without losing precision?

In Python, you cannot directly store a floating-point number as an integer without losing precision. However, you can store the float as a string or a decimal.Decimal object to maintain its precision.

Q5: Can I use the float data type in place of the long data type without any issues?

It depends on the specific problem and the library or function being used. Some operations and libraries, like PyTorch, can handle both float and long data types without any issues. However, others may require specific data types, so it is essential to consult the documentation or source code to ensure compatibility.

Learn more about Python data types
PyTorch data types

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