Python for Chemistry: An introduction to Python algorithms, Simulations, and Programing for Chemistry (English Edition)

CHAPTER 1

Understanding Python Functions for Chemistry

Introduction

Python is the most preferred language for scientific computing since it has not a steep learning curve. It was developed by Guido van Rossum, in 1991. It can be deployed from simple numerical computing or data analysis to complex symbolic computations along with 2D, 3D graphical representations. It can also be used for web-based applications, and it can be installed in Windows, Linux and Mac operating systems. Syntax of the Python is easily understandable. For example, the following syntax shows, addition of two numbers and the syntax used is like the plain English.

b = 2; x = 3

print(Sum of 'b' and 'x' is, (b+x))

>>>

Sum of 'b' and 'x' is 5

Though python language has many built-in functions for scientific computations, this chapter outlines the basic Python functions for computing chemical data such as deploying dictionaries to fetch the atomic mass and atomic number of the chemical elements, estimating atomic percentage from the molecular formula, reading and writing .csv files, computation of thermodynamic, photochemical and chemical kinetics parameters. This chapter also covers the error handlers with reference to electron transfer redox reactions. Algorithm to record the rate of the reaction with timer function is also discussed. Deploying loops and operators in the estimation of various chemical parameters or for simulations are also explained with examples. By using the math module, algorithm for pH metric titrations, determination of energy of activation and spin coupling for NMR spectral data can also be discoursed.

Structure

Dictionary for atomic numbers and atomic masses

Adding elements to the dictionary

Updating elements in the dictionary

Deleting elements from the dictionary

Atomic mass percentage from molecular formula

Data module for physical and chemical constants

Molar gas constant from Boltzmann’s constant

Estimation of volume of an ideal gas

Quantum efficiency of photochemical reactions

Fetching Rf data of amino acids from .csv file

Fetching selective data for amino acids from .csv file

Converting 'amino_acids.csv' to dictionary

Estimation of rate constant with data as a list

Exporting rate constant data to .csv

Math module

Power of 10 (e)

pH metric acid-base titration

R.M.S and average velocity of ideal gas molecules

Rate constant from activation energy

Calculating sine (angle) from radians

Estimating bond length from the bond angle

Priority for arithmetical operators

Quotient and Modulo operators

Assignment operators

Comparison operators

Logical operators

Identity operators

Membership operators

cmath module

Scrutinizing user input data

Tackling of errors in user inputs

Number of electrons transferred in a redox reaction

Conditions and Loops

if … elif … else statements

Error handling with if … else loops

Nested loops

while loops

for loops

range() function

Fetching selective rows of amino_acid.csv file

timer() function

Recording concentration with time (reaction rate)

Recursion

Predicting spin–spin coupling in NMR spectra

Lambda function

Dictionary for atomic numbers and atomic masses

Dictionary is a collection of data (str, int, float formats) and is used to store data as key : values pairs within curled braces, { }. It is ordered, changeable and do not allow duplicates. Based on the key, data values can be fetched. But, in a dictionary new key : values can be added or existing key : values can be updated and can be deleted. Dictionaries can be created for any types of data sets and can be deployed for fetching the required values on program execution. This program demonstrates the creation of a data dictionary for atomic number and atomic masses of the chemical elements based on their symbols as keys.

Syntax: dictionary_name = {key: [value1, value2]}

Following code demonstrates the creation of a dictionary for chemical elements.

# dictionary_name = {symbol: [atomic number, atomic mass]}

atomic_number_mass = {

H : [1, 1.007], # H is key and [1, 1.007] are values.

He : [2, 4.003],

Li : [3, 6.941],

Be : [4, 9.012],

B : [5, 10.812],

C : [6, 12.011],

N : [7, 14.007],

O : [8, 15.999],

F : [9, 18.998],

Ne : [10, 20.18],

Na : [11, 22.99],

Mg : [12, 24.305],

Al : [13, 26.982],

Si : [14, 28.086],

P : [15, 30.974],

S : [16, 32.066],

Cl : [17, 35.453],

Ar : [18, 39.948],

K : [19, 39.098],

Ca : [20, 40.078],

Sc : [21, 44.956],

Ti : [22, 47.867],

V : [23, 50.942],

Cr : [24, 51.996],

Mn : [25, 54.938],

Fe : [26, 55.845],

Co : [27, 58.933],

Ni : [28, 58.693],

Cu : [29, 63.546],

Zn : [30, 65.382],

Ga : [31, 69.723],

Ge : [32, 72.631],

As : [33, 74.922],

Se : [34, 78.963],

Br : [35, 79.904],

Kr : [36, 83.798],

Rb : [37, 85.468],

Sr : [38, 87.621],

Y : [39, 88.906],

Zr : [40, 91.224],

Nb : [41, 92.906],

Mo : [42, 95.962],

Tc : [43, 98],

Ru : [44, 101.072],

Rh : [45, 102.906],

Pd : [46, 106.421],

Ag : [47, 107.868],

Cd : [48, 112.412],

In : [49, 114.818],

Sn : [50, 118.711],

Sb : [51, 121.76],

Te : [52, 127.603],

I : [53, 126.904],

Xe : [54, 131.294],

Cs : [55, 132.905],

Ba : [56, 137.328],

La : [57, 138.905],

Ce : [58, 140.116],

Pr : [59, 140.908],

Nd : [60, 144.242],

Pm : [61, 145],

Sm : [62, 150.362],

Eu : [63, 151.964],

Gd : [64, 157.253],

Tb : [65, 158.925],

Dy : [66, 162.5],

Ho : [67, 164.93],

Er : [68, 167.259],

Tm : [69, 168.934],

Yb : [70, 173.055],

Lu : [71, 174.967],

Hf : [72, 178.492],

Ta : [73, 180.948],

W : [74, 183.841],

Re : [75, 186.207],

Os : [76, 190.233],

Ir : [77, 192.217],

Pt : [78, 195.085],

Au : [79, 196.967],

Hg : [80, 200.592],

Tl : [81, 204.383],

Pb : [82, 207.21],

Bi : [83, 208.98],

Po : [84, 209],

At : [85, 210],

Rn : [86, 222],

Fr : [87, 223],

Ra : [88, 226],

Ac : [89, 227],

Th : [90, 232.038],

Pa : [91, 231.036],

U : [92, 238.029],

Np : [93, 237],

Pu : [94, 244],

Am : [95, 243],

Cm : [96, 247],

Bk : [97, 247],

Cf : [98, 251],

Es : [99, 252],

Fm : [100, 257],

Md : [101, 258],

No : [102, 259],

Lr : [103, 266],

Rf : [104, 267],

Db : [105, 268],

Sg : [106, 269],

Bh : [107, 270],

Hs : [108, 277],

Mt : [109, 278],

Ds : [110, 281],

Rg : [111, 282],

Cn : [112, 285],

Nh : [113, 286],

Fl : [114, 289],

Mc : [115, 290],

Lv : [116, 293],

Ts : [117, 294],

Og : [118, 294]

}

x = input (Enter symbol: ) #user input for symbol (key)

print(Atomic number for , x, is: )

print(atomic_number_mass.get(x)[0]) #index[0] atomic number

print(Atomic mass for , x, is: )

print(atomic_number_mass.get(x)[1]) #index[1] atomic mass

>>>

Enter symbol: F

Atomic number for F is:

9

Atomic mass for F is:

18.998

From the user input for the given key value (as ‘x’ for symbol of elements), respective atomic number as well as atomic mass can be fetched. It must be noted that the index values for this dictionary, (atomic_number_mass) is having only two values [0] for the first item of the list, which is atomic number and [1] for the second item of the list, which is atomic mass. Such dictionaries are used to create modules of data sets of various chemical parameters. It must be noted that if any duplicate key is added, it will be removed.

Adding elements to the dictionary

New data can be added, and existing data can be updated or deleted in the dictionary via key : values.

Adding new elements (keys) into the existing dictionary.

atomic_number_mass = {

H : [1, 1.007],

He : [2, 4.003],

Li : [3, 6.941],

Be : [4, 9.012],

B : [5, 10.812],

C : [6, 12.011],

N : [7, 14.007]    # intentionally limited to N

}

print(len(atomic_number_mass)) # len function to know the number of elements

atomic_number_mass[O] = [8, 15.999] # new key : values

print(atomic_number_mass) # display new dictionary

print(len(atomic_number_mass))

>>>

7

{'H': [1, 1.007], 'He': [2, 4.003], 'Li': [3, 6.941], 'Be': [4, 9.012], 'B': [5, 10.812], 'C': [6, 12.011], 'N': [7, 14.007], 'O': [8, 15.999]}

8

Updating elements in the dictionary

Modifying the keys and their values in the existing keys of the dictionary and their values is depicted as following:

atomic_number_mass = {

H : [1, 1.007],

He : [2, 4.003],

Li : [3, 6.941],

Be : [4, 9.012],

B : [5, 10.812],

C : [6, 12.011],

N : [7, 14.007]    # intentionally limited to N

}

atomic_number_mass[C] = [6, 13.013]  # updating the key C values.

print(atomic_number_mass)

>>>

{‘H’: [1, 1.007], ‘He’: [2, 4.003], ‘Li’: [3, 6.941], ‘Be’: [4, 9.012], ‘B’: [5, 10.812], ‘C’: [6, 13.013], ‘N’: [7, 14.007]}

Deleting elements from the dictionary

With del name_of_dictionary[key] the given key and its values can be deleted.

atomic_number_mass = {

H : [1, 1.007],

He : [2, 4.003],

Li : [3, 6.941],

Be : [4, 9.012],

B : [5, 10.812],

C : [6, 12.011],

N : [7, 14.007]    # intentionally limited to 'N'

}

del atomic_number_mass[N]   # removes 'N' and its values

print(atomic_number_mass)

>>>

{'H': [1, 1.007], 'He': [2, 4.003], 'Li': [3, 6.941], 'Be': [4, 9.012], 'B': [5, 10.812], 'C': [6, 12.011]}

Deleting a key can also be executed by pop command as: atomic_number_mass.pop (N) also gives the same output. Using the keyword, del the dictionary can be deleted.

del atomic_number_mass # This deletes the dictionary

Atomic mass percentage from molecular formula

From a dictionary, key: value data sets of string, float, integer, Boolean for various chemical parameters can be fetched for real-time calculations. Hence the designed dictionary can be deployed for real-time applications.

Based on the dictionary in program # 1, it is possible to calculate various basic data such as molar mass or number of moles of compounds.

This program demonstrates the calculation of molar mass and atomic mass percentage of individual elements of the given compound based on the molecular formula as user input.

# Creating a dictionary for each element with atomic numbers and atomic masses.

# With RegEx module, segregating atoms and their counts for the given compound.

# Splitting of atoms as string from the user input of molecular formula via Uppercase.

# Counting of individual atoms followed by multiplication with its atomic mass fetched from dictionary.

# Interconversion of float and string followed by summation of the individual atomic masses.

# Loop to calculate atomic mass and atomic mass % of atoms.

loop_value = 0    # for infinite loop

while loop_value == 0:   # indentation for loop

atomic_number_mass = {   # dictionary

H : [1, 1.007],

He : [2, 4.003],

Li : [3, 6.941],

Be : [4, 9.012],

B : [5, 10.812],

C : [6, 12.011],

N : [7, 1.007],

# Dictionary of elements with atomic number and the relevant atomic mass:

O : [8, 15.999],

F : [9, 18.998],

Ne : [10, 20.18],

Na : [11, 22.99],

Mg : [12, 24.305],

Al : [13, 26.982],

Si : [14, 28.086],

P : [15, 30.974],

S : [16, 32.066],

Cl : [17, 35.453],

Ar : [18, 39.948],

K : [19, 39.098],

Ca : [20, 40.078],

Sc : [21, 44.956],

Ti : [22, 47.867],

V : [23, 50.942],

Cr : [24, 51.996],

Mn : [25, 54.938],

Fe : [26, 55.845],

Co : [27, 58.933],

Ni : [28, 58.693],

Cu : [29, 63.546],

Zn : [30, 65.382],

Ga : [31, 69.723],

Ge : [32, 72.631],

As : [33, 74.922],

Se : [34, 78.963],

Br : [35, 79.904],

Kr : [36, 83.798],

Rb : [37, 85.468],

Sr : [38, 87.621],

Y : [39, 88.906],

Zr : [40, 91.224],

Nb : [41, 92.906],

Mo : [42, 95.962],

Tc : [43, 98],

Ru : [44, 101.072],

Rh : [45, 102.906],

Pd : [46, 106.421],

Ag : [47, 107.868],

Cd : [48, 112.412],

In : [49, 114.818],

Sn : [50, 118.711],

Sb : [51, 121.76],

Te : [52, 127.603],

I : [53, 126.904],

Xe : [54, 131.294],

Cs : [55, 132.905],

Ba : [56, 137.328],

La : [57, 138.905],

Ce : [58, 140.116],

Pr : [59, 140.908],

Nd : [60, 144.242],

Pm : [61, 145],

Sm : [62, 150.362],

Eu : [63, 151.964],

Gd : [64, 157.253],

Tb : [65, 158.925],

Dy : [66, 162.5],

Ho : [67, 164.93],

Er : [68, 167.259],

Tm : [69, 168.934],

Yb : [70, 173.055],

Lu : [71, 174.967],

Hf : [72, 178.492],

Ta : [73, 180.948],

W : [74, 183.841],

Re : [75, 186.207],

Os : [76, 190.233],

Ir : [77, 192.217],

Pt : [78, 195.085],

Au : [79, 196.967],

Hg : [80,