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SciPy – Constants

  • Last Updated : 13 Jan, 2022

Scipy stands for Scientific Python and in any Scientific/Mathematical calculation, we often need universal constants to carry out tasks, one famous example is calculating the Area of a circle = ‘pi*r*r’ where PI = 3.14… or a more complicated one like finding forcegravity = G*M*m ⁄ (distance)2 where G = gravitational constant. In all such scenarios, it would be very handy if we have reference material to look up these constants and incorporate them into our calculation with ease.

Scipy-Constants is a sub-module inside the Scipy library that does this for us. It contains an exhaustive list of universal mathematical constants, Physical constants, and units. which can be looked up with just 1 line of code.

Accessing Constants

Just type the name of the constant in place of XXXX in ‘scipy.constants.XXXX‘ format to access its value. Below listed are a few most important constants using scipy.constant module down below. The list is not exhaustive, but it gives a good idea of how to access constants.  

Python3




# import module
import scipy
 
# Just type the name of the constant in
# scipy.constant.XXXX format to access its value.
print("sciPy - pi:", scipy.constants.pi)
print("Golden ratio:", scipy.constants.golden_ratio)
print("Speed of light in vacuum:", scipy.constants.c)
print("Gravitational Constant:", scipy.constants.G)
print("Molar Gas Constant:", scipy.constants.R)
print("Boltzman Constant:", scipy.constants.k)
print("Proton mass Constant:", scipy.constants.proton_mass)

Output:

Finding Constants

We can use an inbuilt method to find the constants relevant to our use case. Constants are stored using a dictionary data structure, and we can use the scipy. constants.find() API to find all relevant constants from the dict and use them accordingly. 

The code below demonstrates using scipy. constants.find() API. The below code prints all constants which contain the ‘electron’ word in it, and we can filter out the one which is required. 

Python3




import scipy
 
 
# find method looks up in the dictorary and
# finds out all the constants containing
# 'electron' word in it and returns a list
# of constants.
res = scipy.constants.find("electron")
print(res, end='\n')

Output:

Not just the magnitude of a constant we can also access the unit and degree of uncertainty associated with the magnitude of any physical_constants stored in scipy.constants module, using the format 

physical_constants[name] = (value, unit, uncertainty).

Python3




import scipy
 
 
# This returns a tuple (value, unit, uncertainty)
# associated with the physical constant
print(scipy.constants.physical_constants['alpha particle mass'])

Output: 

(6.6446573357e-27, 'kg', 2e-36)

Example:

Python3




import scipy
 
# Area of a circle using
# scipy.constants.pi
def Area_of_Circle(r):
    return scipy.constants.pi * r * r
 
# Calculates the gravational for
def force_gravity(M, m, dist):
    return (scipy.constants.G*M*m) / (dist**2)
 
 
print(f'Area of Circle: {Area_of_Circle(5)}')
print(f'Gravitational force: {force_gravity(10,5,1)}')

Output:

Apart from the above variables, scipy.constants also contain more physical constants, and below is a list of all methods available in scipy.constants module with an explanation.

Below are the most commonly used constants available in SciPy module:

ConstantsDescription
piMathematical pi value
goldenMathematicalgolden ratio
cSpeed of light in vacuum
speed_of_lightSpeed of light in vacuum
GStandard acceleration of gravity
GNewton Constant of gravitation
EElementary charge
RMolar gas constant
AlphaFine-structure constant
N_AAvagadro constant
KBoltzmann constant
SigmaStefan-Boltzmann constant σ
m_eElectron mass
m_pProton mass
m_nNeutron Mass
HPlank Constant
Plank constantPlank constant h

Below are the unit constants available in the SciPy module:

  • Mass:
UnitDescription
GramOne gram in Kilogram.
GrainOne grain in Kilogram.
PoundOne Pound in Kilogram.
OunceOne Ounce in Kilogram.
automic_massAtomics mass constant in Kilogram.
  • Time:
UnitDescription
MinuteOne minute in seconds.
HourOne hour in seconds.
DayOne day in seconds.
YearOne year in seconds.
  • Length:
UnitsDescription
InchOne inch in meters.
FootOne foot in meters.
YardOne yard in meters.
PtOne point in meters.
MicronOne Micron in meters.
  • Pressure:
UnitsDescription
AtmThe standard atmosphere in pascals.
AtmosphereThe standard atmosphere in pascals.
BarOne bar in Pascals.
TorrOne torr(mmHg) in pascals.
  • Area:
UnitsDescription
HectareOne hectare in square meters.
AcreOne acre in square meters.
  • Speed:
UnitsDescription
KmhKilometer per hour in meter per second.
MphMiles per hour in meter per second.
MachOne Match in meter per second.

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