Python math module

Question

Whenever I try to use any of the built-in functions of Python's exponentiation and logarithms module, I get an error like this:

NameError: name 'sqrt' is not defined

I have tried using math.sqrt(4),sqrt(4) and sqrt(4.0), but none of them work. The exception is pow, which works as it's supposed to. This is really strange and I'm not sure what's wrong.

if the function is not a built-in, you have to import the module it is contained in. See [python library](http://docs.python.org/library/), and the [list of built-ins](http://docs.python.org/library/functions.html). — President James K. Polk, Jan 09 '12 at 02:22
I'm trying to imagine a scenario where you wouldn't want _math_ to be imported automatically on startup. [Python: Is there a place when I can put default imports for all my modules?](https://stackoverflow.com/q/1350887/86967) — Brent Bradburn, Apr 18 '22 at 14:09

score 57 · Accepted Answer · answered Jan 09 '12 at 02:19

57

pow is built into the language(not part of the math library). The problem is that you haven't imported math.

Try this:

import math
math.sqrt(4)

answered Jan 09 '12 at 02:19

dave

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score 18 · Answer 2 · answered Mar 04 '14 at 11:41

18

You can also import as

from math import *

Then you can use any mathematical function without prefixing math. e.g.

sqrt(4)

answered Mar 04 '14 at 11:41

Softec

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But be aware that the [Style Guide for Python Code](https://peps.python.org/pep-0008/) says: "Wildcard imports (`from import *`) should be avoided, as they make it unclear which names are present in the namespace, confusing both readers and many automated tools.". – Matthias Jun 29 '23 at 05:31

score 5 · Answer 3 · edited May 17 '20 at 03:18

5

add:

import math

at beginning. and then use:

math.sqrt(num)  # or any other function you deem neccessary

edited May 17 '20 at 03:18

Unmitigated

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answered Jan 10 '12 at 14:15

Arnab Ghosal

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score 2 · Answer 4 · answered Jan 09 '12 at 02:19

You need to say math.sqrt when you use it. Or, do from math import sqrt.

Hmm, I just read your question more thoroughly.... How are you importing math? I just tried import math and then math.sqrt which worked perfectly. Are you doing something like import math as m? If so, then you have to prefix the function with m (or whatever name you used after as).

pow is working because there are two versions: an always available version in __builtin__, and another version in math.

score 1 · Answer 5 · answered Jul 12 '18 at 17:35

1

import math #imports math module

import math as m
print(m.sqrt(25))

from math import sqrt #imports a method from math module
print(sqrt(25))

from math import sqrt as s
print(s(25))

from math import *
print(sqrt(25))

answered Jul 12 '18 at 17:35

Kalyan Pendyala

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score 0 · Answer 6 · answered Jul 03 '17 at 06:29

0

In

from math import sqrt

Using sqrt(4) works perfectly well. You need to only use math.sqrt(4) when you just use "import math".

answered Jul 03 '17 at 06:29

Abhishek

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score 0 · Answer 7 · edited Feb 18 '21 at 20:48

0

import math as m
a=int(input("Enter the no"))
print(m.sqrt(a))

from math import sqrt
print(sqrt(25))

from math import sqrt as s
print(s(25))

from math import *
print(sqrt(25))

All works.

edited Feb 18 '21 at 20:48

Lucas

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answered Apr 23 '19 at 10:59

Rishabh Sharma

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Dont put the code directly. Provide explanation. Go through this [link](https://stackoverflow.com/help/how-to-answer) to answer better – Sumanth Shastry Apr 23 '19 at 11:03

Python math module

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