Converting data from fortran to python

Question

I'm new to programming and now I'm trying to rewrite the Fortran code in Python script.

In original fortran code, it declares real number as:

Begin
c----
      data (A(0,i), i=0,17)   
     &  /
     &    9.526e5, 1.416e6, 1.210e6, 7.734e5, 4.050e5, 1.851e5,
     &    7.944e4, 3.382e4, 1.434e4, 5.821e3, 2.174e3, 7.392e2,
     &    2.349e2, 7.361e1, 2.405e1, 8.423e0, 3.120e0, 1.176e0
     &  /
c----
c---- End

Here how can I convert this A_ul(0,i) in python code? And how can i rewrite A(0,i) to calculate :

B = (p**2)*(c**3)*A_ul(0,i)

Such that p and c are constants

Welcome, I suggest taking the tour. Please use tag fortran for all Fortran-related questions. — Vladimir F Героям слава
– Vladimir F Героям слава, Commented Apr 24, 2020 at 10:25
To anyone answering this with Python code or reading the answers, please note that the Fortran data statement isn't the same thing as an assignment statement. Simply writing a Python assignment isn't going to capture all complexity of this Fortran snippet. — francescalus
– francescalus, Commented Apr 24, 2020 at 12:13

DarrylG · Accepted Answer · 2020-04-24 10:23:38Z

Two Choices

Option 1: Using Normal Python Lists

Python List Comprehension Tutorial

A_ul = [9.526e5, 1.416e6, 1.210e6, 7.734e5, 4.050e5, 1.851e5,
        7.944e4, 3.382e4, 1.434e4, 5.821e3, 2.174e3, 7.392e2,
        2.349e2, 7.361e1, 2.405e1, 8.423e0, 3.120e0, 1.176e0]

# some values for p, c (assuming scalars)
p = 2.95
c = 3.41

# generate computation of scalar with array using list comprehension
B = [(p**2)*(c**3)*x for x in A_ul] 

print(B)

Out

[328713655.56773156, 488619080.70954007, 417534666.42552507, 266877116.54008356, 139753338.76226252, 63872451.863937765, 27412358.595738605, 11670266.461579552, 4948303.402100851, 2008652.308481803, 750182.1196769351, 255075.72348904808, 81056.93648211227, 25400.60065750653, 8298.932832672626, 2906.524376282808, 1076.6183134278003, 405.80228736894003]

Option 2: Using Python Numpy Arrays

Numpy allows easy array and matrix expressions in Python (i.e. an alternative to Matlab)

Numpy tutorial

import numpy as np

# A_ul as Numpy array
A_ul = np.array([9.526e5, 1.416e6, 1.210e6, 7.734e5, 4.050e5, 1.851e5,
        7.944e4, 3.382e4, 1.434e4, 5.821e3, 2.174e3, 7.392e2,
        2.349e2, 7.361e1, 2.405e1, 8.423e0, 3.120e0, 1.176e0])
# some values for p, c (assuming scalars)
p = 2.95
c = 3.41

# numpy understands multiplying scalars by arrays
B = (p**2)*(c**3)*A_ul 

print(B)

Out

[3.28713656e+08 4.88619081e+08 4.17534666e+08 2.66877117e+08
 1.39753339e+08 6.38724519e+07 2.74123586e+07 1.16702665e+07
 4.94830340e+06 2.00865231e+06 7.50182120e+05 2.55075723e+05
 8.10569365e+04 2.54006007e+04 8.29893283e+03 2.90652438e+03
 1.07661831e+03 4.05802287e+02]

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