SciPy - Constants

SciPy constants package provides a wide range of constants, which are used in the general scientific area.

SciPy Constants Package

The scipy.constants package provides various constants. We have to import the required constant and use them as per the requirement. Let us see how these constant variables are imported and used.

To start with, let us compare the ‘pi’ value by considering the following example.

#Import pi constant from both the packages
from scipy.constants import pi
from math import pi

print("sciPy - pi = %.16f"%scipy.constants.pi)
print("math - pi = %.16f"%math.pi)

The above program will generate the following output.

sciPy - pi = 3.1415926535897931
math - pi = 3.1415926535897931

List of Constants Available

The following tables describe in brief the various constants.

Mathematical Constants

Sr. No. Constant Description
1 pi pi
2 golden Golden Ratio

Physical Constants

The following table lists the most commonly used physical constants.

Sr. No. Constant & Description
1

c

Speed of light in vacuum

2

speed_of_light

Speed of light in vacuum

3

h

Planck constant

4

Planck

Planck constant h

5

G

Newton’s gravitational constant

6

e

Elementary charge

7

R

Molar gas constant

8

9

k

Boltzmann constant

10

electron_mass(OR) m_e

Electronic mass

11

proton_mass (OR) m_p

Proton mass

12

neutron_mass(OR)m_n

Neutron mass

Units

The following table has the list of SI units.

Sr. No. Unit Value
1 milli 0.001
2 micro 1e-06
3 kilo 1000

These units range from yotta, zetta, exa, peta, tera ……kilo, hector, …nano, pico, … to zepto.

Other Important Constants

The following table lists other important constants used in SciPy.

Sr. No. Unit Value
1 gram 0.001 kg
2 atomic mass Atomic mass constant
4 minute One minute in seconds
5 day One day in seconds
6 inch One inch in meters
7 micron One micron in meters
8 light_year One light-year in meters
9 atm Standard atmosphere in pascals
10 acre One acre in square meters
11 liter One liter in cubic meters
12 gallon One gallon in cubic meters
13 kmh Kilometers per hour in meters per seconds
14 degree_Fahrenheit One Fahrenheit in kelvins
15 eV One electron volt in joules
16 hp One horsepower in watts
17 dyn One dyne in newtons
18 lambda2nu Convert wavelength to optical frequency

Remembering all of these are a bit tough. The easy way to get which key is for which function is with the scipy.constants.find() method. Let us consider the following example.

import scipy.constants
res = scipy.constants.physical_constants["alpha particle mass"]
print res

The above program will generate the following output.

[
'alpha particle mass',
'alpha particle mass energy equivalent',
'alpha particle mass energy equivalent in MeV',
'alpha particle mass in u',
'electron to alpha particle mass ratio'
]

This method returns the list of keys, else nothing if the keyword does not match.