• 0 Vote(s) - 0 Average
• 1
• 2
• 3
• 4
• 5
[Tut] Python Math Domain Error (How to Fix This Stupid Bug)

Python Math Domain Error (How to Fix This Stupid Bug)

You may encounter a special `ValueError` when working with Python’s `math` module.

`ValueError: math domain error`

Python raises this error when you try to do something that is not mathematically possible or mathematically defined.

To understand this error, have a look at the definition of the domain:

The domain of a function is the complete set of possible values of the independent variable. Roughly speaking, the domain is the set of all possible (input) x-values which result in a valid (output) y-value.” (source)

The domain of a function is the set of all possible input values. If Python throws the `ValueError: math domain error`, you’ve passed an undefined input into the `math` function. Fix the error by passing a valid input for which the function is able to calculate a numerical output.

Here are a few examples:

## Python Math Domain Error Sqrt

The math domain error appears if you pass a negative argument into the `math.sqrt()` function. It’s mathematically impossible to calculate the square root of a negative number without using complex numbers. Python doesn’t get that and throws a `ValueError: math domain error`.

Here’s a minimal example:

```from math import sqrt
print(sqrt(-1)) '''
Traceback (most recent call last): File "C:\Users\xcent\Desktop\Finxter\Blog\code.py", line 2, in <module> print(sqrt(-1))
ValueError: math domain error '''```

You can fix the math domain error by using the `cmath` package that allows the creation of complex numbers:

```from cmath import sqrt
print(sqrt(-1))
# 1j```

## Python Math Domain Error Log

The `math domain error` for the `math.log()` function appears if you pass a zero value into it—the logarithm is not defined for value 0.

Here’s the code on an input value outside the domain of the logarithm function:

```from math import log
print(log(0))```

The output is the math domain error:

```Traceback (most recent call last): File "C:\Users\xcent\Desktop\Finxter\Blog\code.py", line 3, in <module> print(log(0))
ValueError: math domain error```

You can fix this error by passing a valid input value into the `math.log()` function:

```from math import log
print(log(0.000001))
# -13.815510557964274```

This error can sometimes appear if you pass a very small number into it—Python’s float type cannot express all numbers. To pass a value “close to 0”, use the `Decimal` module with higher precision, or pass a very small input argument such as:

`math.log(sys.float_info.min)`

## Python Math Domain Error Acos

The `math domain error` for the `math.acos()` function appears if you pass a value into it for which it is not defined—arccos is only defined for values between -1 and 1.

Here’s the wrong code:

```import math
print(math.acos(2))```

The output is the math domain error:

```Traceback (most recent call last): File "C:\Users\xcent\Desktop\Finxter\Blog\code.py", line 3, in <module> print(math.acos(2))
ValueError: math domain error```

You can fix this error by passing a valid input value between [-1,1] into the `math.acos()` function:

```import math
print(math.acos(0.5))
# 1.0471975511965979```

## Python Math Domain Error Asin

The `math domain error` for the `math.asin()` function appears if you pass a value into it for which it is not defined—arcsin is only defined for values between -1 and 1.

Here’s the erroneous code:

```import math
print(math.asin(2))```

The output is the math domain error:

```Traceback (most recent call last): File "C:\Users\xcent\Desktop\Finxter\Blog\code.py", line 3, in <module> print(math.asin(2))
ValueError: math domain error```

You can fix this error by passing a valid input value between [-1,1] into the `math.asin()` function:

```import math
print(math.asin(0.5))
# 0.5235987755982989```

## Python Math Domain Error Pow

The `math domain error` for the `math.pow(a,b)` function to calculate a**b appears if you pass a negative base value into it and try to calculate a negative power of it. The reason it is not defined is that any negative number to the power of 0.5 would be the square number—and thus, a complex number. But complex numbers are not defined by default in Python!

```import math
print(math.pow(-2, 0.5))```

The output is the math domain error:

```Traceback (most recent call last): File "C:\Users\xcent\Desktop\Finxter\Blog\code.py", line 3, in <module> print(math.pow(-2, 0.5))
ValueError: math domain error```

If you need a complex number, ab must be rewritten into eb ln a. For example:

```import cmath
print(cmath.exp(0.5 * cmath.log(-2)))
# (8.659560562354932e-17+1.414213562373095j)```

You see, it’s a complex number!

## NumPy Math Domain Error — np.log(x)

```import numpy as np
import matplotlib.pyplot as plt # Plotting y = log(x)
fig, ax = plt.subplots()
ax.set(xlim=(-5, 20), ylim=(-4, 4), title='log(x)', ylabel='y', xlabel='x')
x = np.linspace(-10, 20, num=1000)
y = np.log(x) plt.plot(x, y)```

This is the graph of `log(x)`. Don’t worry if you don’t understand the code, what’s more important is the following point. You can see that log(x) tends to negative infinity as x tends to 0. Thus, it is mathematically meaningless to calculate the log of a negative number. If you try to do so, Python raises a math domain error.

```>>> math.log(-10)
Traceback (most recent call last): File "<stdin>", line 1, in <module>
ValueError: math domain error```

## Where to Go From Here?

Enough theory, let’s get some practice!

To become successful in coding, you need to get out there and solve real problems for real people. That’s how you can become a six-figure earner easily. And that’s how you polish the skills you really need in practice. After all, what’s the use of learning theory that nobody ever needs?

Practice projects is how you sharpen your saw in coding!

Do you want to become a code master by focusing on practical code projects that actually earn you money and solve problems for people?

Then become a Python freelance developer! It’s the best way of approaching the task of improving your Python skills—even if you are a complete beginner.

Join my free webinar “How to Build Your High-Income Skill Python” and watch how I grew my coding business online and how you can, too—from the comfort of your own home.

Join the free webinar now!

The post Python Math Domain Error (How to Fix This Stupid Bug) first appeared on Finxter.

https://www.sickgaming.net/blog/2020/11/...tupid-bug/

 Possibly Related Threads… Thread Author Replies Views Last Post [Tut] The Math of Becoming a Millionaire in 13 Years xSicKxBot 0 38 04-05-2021, 10:06 AM Last Post: xSicKxBot [Tut] Top 10 Python Math Cheat Sheets. xSicKxBot 0 83 02-07-2021, 04:38 AM Last Post: xSicKxBot [Tut] Python complex() — A Useless Python Feature? xSicKxBot 0 95 12-19-2020, 02:05 AM Last Post: xSicKxBot [Tut] Python TypeError: Object is Not Subscriptable (How to Fix This Stupid Bug) xSicKxBot 0 97 11-13-2020, 12:04 AM Last Post: xSicKxBot [Tut] Python’s NameError: name ‘xxx’ is not defined — How to Fix This Stupid Bug? xSicKxBot 0 172 10-16-2020, 10:30 PM Last Post: xSicKxBot [Tut] Python IndentationError: unexpected indent (How to Fix This Stupid Bug) xSicKxBot 0 171 10-10-2020, 08:24 PM Last Post: xSicKxBot [Tut] Python Import Error (ModuleNotFoundError) xSicKxBot 0 111 09-20-2020, 04:15 PM Last Post: xSicKxBot [Tut] Python Unicode Encode Error xSicKxBot 0 111 09-19-2020, 03:25 PM Last Post: xSicKxBot [Tut] Hello World! A Python One-Liner to Get Started with Python Quickly xSicKxBot 0 137 09-07-2020, 06:10 PM Last Post: xSicKxBot [Tut] Python Join List of Bytes (and What’s a Python Byte Anyway?) xSicKxBot 0 212 06-10-2020, 05:38 AM Last Post: xSicKxBot

Forum Jump:

 Active Threads [Tut] Iterating Through a Range of Dates... Last Post: xSicKxBot Yesterday 09:18 PM » Replies: 0 » Views: 3 (Indie Deal) FREE Super Panda Adventures... Last Post: xSicKxBot Yesterday 09:18 PM » Replies: 0 » Views: 3 Mobile - RuneScape Mobile – what Jagex l... Last Post: xSicKxBot Yesterday 09:18 PM » Replies: 0 » Views: 3 ASP.NET Core 6 and Authentication Server... Last Post: xSicKxBot Yesterday 09:18 PM » Replies: 0 » Views: 3 AppleInsider - Mj Rodriguez joins Apple ... Last Post: xSicKxBot Yesterday 09:17 PM » Replies: 0 » Views: 4 News - Random: This Minecraft Version Of... Last Post: xSicKxBot Yesterday 09:17 PM » Replies: 0 » Views: 3 News - Don't Miss Vinny, Alex, And Brad'... Last Post: xSicKxBot Yesterday 09:17 PM » Replies: 0 » Views: 34 Xbox Wire - Xbox and NTWRK Collaborate t... Last Post: xSicKxBot Yesterday 02:05 PM » Replies: 0 » Views: 5 News - Nintendo Game Builder Garage Game... Last Post: xSicKxBot Yesterday 02:05 PM » Replies: 0 » Views: 54 News - Get a job: Join Talofa Games as a... Last Post: xSicKxBot Yesterday 02:05 PM » Replies: 0 » Views: 53

 Twitter Tweets by _SickGaming