Use python to process and create input files for external software

Question

When I program, I often use external software to do heavy computing, but then analyze the results in Python. These external programs are often Fortran, C, or C ++ that work by providing them with input files. This can be either a small file indicating which mode performs certain calculations, or a large data file that it should process. These files often use a specific format (there are so many spaces between data columns). For example, the following is for the data file that I am currently using.

This is a header. The first line is always a header...
  7352.103      26.0      2.61    -8.397                         11.2
  7353.510      26.0      4.73    -1.570                          3.5
  7356.643      26.0      5.75    -2.964                          9.0
  7356.648      26.0      5.35    -3.187                          9.0
  7364.034      26.0      5.67    -5.508                          1.7
  7382.523      26.0      5.61    -3.935                          1.9

My question is: is there a Python library for creating such input files, from reading a template (specified by an employee or from external software documentation)?

Usually I have all the columns in a format NumPyand want to give it to a function that creates an input file using an example template. I am not looking for a brute force method that can become ugly very quickly.

I am not sure what to look for here, and any help is appreciated.

Answer 1

savetxt. fmt , FORTRAN . , FORTRAN C.

import numpy as np

example = """
This is a header. The first line is always a header...
  7352.103      26.0      2.61    -8.397                         11.2
...
"""

lines = example.split('\n')[1:]
header = lines[0]
data = []
for line in lines[1:]:
  if len(line):
    data.append([float(x) for x in line.split()])
data = np.array(data)

fmt = '%10.3f %9.1f %9.2f %9.3f %20.1f'  # similar to a FORTRAN format statment
filename = 'stack21865757.txt'

with open(filename,'w') as f:
  np.savetxt(f, data, fmt, header=header)

with open(filename) as f:
  print f.read()

:

# This is a header. The first line is always a header...
  7352.103      26.0      2.61    -8.397                 11.2
  7353.510      26.0      4.73    -1.570                  3.5
...

script, :

import re
tmplt = '  7352.103      26.0      2.61    -8.397                         11.2'
def fmt_from_template(tmplt):
    pat = r'( *-?\d+\.(\d+))' # one number with its decimal
    fmt = []
    while tmplt:
        match = re.search(pat,tmplt)
        if match:
            x = len(match.group(1)) # length of the whole number
            d = len(match.group(2)) # length of decimals
            fmt += ['%%%d.%df'%(x,d)]
            tmplt = tmplt[x:]
    fmt = ''.join(fmt)
    return fmt
print fmt_from_template(tmplt)
# %10.3f%10.1f%10.2f%10.3f%29.1f

Answer 2

hpaulj andwer, fmt savetxt

from __future__ import print_function
import numpy as np
import re
example = """
This is a header. The first line is always a header...
  7352.103      26.0      2.61    -8.397                         11.2
  7353.510      26.0      4.73    -1.570                          3.5
  7356.643      26.0      5.75    -2.964                          9.0
  7356.648      26.0      5.35    -3.187                          9.0
  7364.034      26.0      5.67    -5.508                          1.7
  7382.523      26.0      5.61    -3.935                          1.9
"""
def extract_format(line):
  def iter():
    for match in re.finditer(r"\s+-?\d+\.(\d+)",line):
      yield "%{}.{}f".format(len(match.group(0)),len(match.group(1)))
  return "".join(iter())

lines = example.split('\n')[1:]
header = lines[0]
data = []
for line in lines[1:]:
  if len(line):
    data.append([float(x) for x in line.split()])
data = np.array(data)

fmt = extract_format(lines[1])  # similar to a FORTRAN format statment

filename = 'stack21865757.txt'

with open(filename,'w') as f:
  print(header,file=f)
  np.savetxt(f, data, fmt)

with open(filename) as f:
  print (f.read())

This is a header. The first line is always a header...
  7352.103      26.0      2.61    -8.397                         11.2
  7353.510      26.0      4.73    -1.570                          3.5
  7356.643      26.0      5.75    -2.964                          9.0
  7356.648      26.0      5.35    -3.187                          9.0
  7364.034      26.0      5.67    -5.508                          1.7
  7382.523      26.0      5.61    -3.935                          1.9

Answer 3

, pandas. , . , , .

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