Recoding from C to Python

Question

I'm pretty much a layman in C and I'm learning Python. I need to write the routine described below (in C) for Python:

#include <stdio.h>
#include <math.h>

main()
{
    float   hold[26], hnew[26];
    float   dt, dx;
    float   t, s;
    float   ho;
    float   time;
    float   f1, d2h;

    int i;
    int nx, nlx;
    int n, nend;
    int kount, kprint;


    dt  = 5.0;
    dx  = 10.0;
    t   = 0.02;
    s   = 0.002;
    nx  = 11;
    nlx = nx-1;


    ho = 16.0;
    for( i = 1;  i <= nx;  i++ )
    {
        hold[i] = ho;
        hnew[i] = ho;
    }

    hold[nx] = 11.0;

    printf("\t\t\t\thead\t\t\t\t      time\n\n");
    kount  = 1;
    kprint = 2;

    time = dt;
    nend = 100;


    for( n = 1;  n <= nend;  n++ )
    {
            /* update solution */

        for( i = 2;  i <= nlx;  i++ )
        {
            f1 = dt*t/s;
            d2h = ( hold[i+1] - 2.0*hold[i] + hold[i-1])/(dx*dx);
            hnew[i] = hold[i] + (f1*d2h);
        }

        for( i = 1;  i <= nlx;  i++ )
        {
            hold[i] = hnew[i];
        }


        if( kount == kprint )
        {
            for( i = 1;  i <= nx;  i++ )
            {
                printf(" %.2f",hold[i]);
            }
            printf("   %6.2f\n",time);
            kount = 0;
        }

        time  = time + dt;
        kount = kount + 1;
    }
}

This is my attempt at Python:

import numpy as np
dt = 5.0
dx = 10.0
t = 0.02
s = 0.002
nx = 11
nlx = nx - 1
ho = 16.0

hold = np.zeros(nx+1)
hnew = np.zeros(nx+1)

for i in range(nx):
    hold[i] = ho
    hnew[i] = ho

hold[nx] = 11.0

However, I can't get over this because I don't know the Python correspondent of the printf function. What would be the correct form of this function in Python? What does it reffer to?

as an aside, using numpy for this doesn't make any sense, at least not in the way you are using it. — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Jul 23, 2019 at 18:21

tim · Accepted Answer · 2019-07-23 18:11:04Z

2

Just print() in Python with .format.

For example:

x, y = 1, 2

print("x = {0}, y = {1}".format(x, y))

Here's the doc

answered Jul 23, 2019 at 18:11

tim

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Chris Charley · Accepted Answer · 2019-07-23 19:00:32Z

2

To print similar to C's printf, the following is an example:

f = 3.25645
g = 3.14159265358979

for fl in (f,g):
    print(f'{fl:.2f}')


3.26
3.14

The first f in the print is the format specifier. The f in the braces says to consider the number as a float.

edited Jul 23, 2019 at 19:00

answered Jul 23, 2019 at 18:38

Chris Charley

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1 Comment

Antti Haapala Over a year ago

The last sentence is incorrect. Format strings do absolutely not support "consider number as a float" - they're formatting instructions for a float.

tim · Accepted Answer · 2019-07-23 18:42:10Z

0

it just print() (see a small program below)

squares = []
for x in range(14):
 squares.append(x**2)

squares

squares2 = [x**2 for x in range(100)]

print (squares2)

edited Jul 23, 2019 at 18:42

tim

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answered Jul 23, 2019 at 18:14

joep

1

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