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?

• Scott Hunter: "What does it refer to?" -- what does this mean?
• Eugene Sh.: Have you tried print ?
• Alex Reynolds: pyformat.info
• Sthln: What is the function of printf in the code?
• juanpa.arrivillaga: as an aside, using numpy for this doesn't make any sense, at least not in the way you are using it.

Answer 1

Just print() in Python with .format.

For example:

x, y = 1, 2
print("x = {0}, y = {1}".format(x, y))

Here's the doc

Answer 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.

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

Answer 3

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)