Simple Fortran 90 to Python conversion by string manipulations:
1. Replacement of Fortran statements with corresponding Python statements
2. Replacement of math functions
3. Commenting out Fortan-specific statment (e.g. integer, end do)
4. Conversion of do loops to for loops: do j=1, M, 2 => for j in range(0, M, 2)
5. Covertion of array access from ( ) to [ ]
6. Conversion of function headers (possibly multi-line)
The resulting file still require some manual cleanup and formatting.
List of substitution pairs for statements.
map_list=[('!','#'),
('\t',' '),
('.d0','.0'),
('d0','0'),
('.eq.',' == '),
('.ne.',' != '),
('/=',' != '),
('.lt.',' < '),
('.gt.',' > '),
('.le.',' <= '),
('.ge.',' >= '),
('then',':'),
('else if','elif'),
('else','else:'),
('&','\\'),
('.and.',' and '),
('.or.',' or '),
('.true.',' True '),
('.false.',' False '),
('end if',''),
('do while','while'),
('end do',''),
('end program','# end program'),
('end function','# end function'),
('end subroutine','# end subroutine'),
('end','# end'),
('program','def'),
('function','def'),
('subroutine','def'),
('integer','#integer'),
('real','#real'),
('allocate','#allocate'),
]
List of substitution pairs for math functions (incomplete).
math_list=[
('dabs','abs'),
('dsqrt','math.sqrt'),
('dlog','math.log'),
('dexp','math.exp'),
]
def file2list(fname, include_eol=False):
''' text file to list of string '''
with open(fname, encoding="utf8") as f:
if include_eol:
content = f.readlines() # \n is included
else:
content = f.read().splitlines() # \n is not included
return content
def ireplace(old, new, text):
''' Case Insensitive Replace excluding comments
based on
http://stackoverflow.com/questions/919056/python-case-insensitive-replace
'''
idx = 0
lim = text.find('#')
if lim < 0:
lim = len(text)
while idx < lim:
# while idx < len(text):
index_l = text.lower().find(old.lower(), idx)
if index_l == -1:
return text
text = text[:index_l] + new + text[index_l + len(old):]
idx = index_l + len(old)
return text
def replace_statements(content,map_list):
''' replaice all statements in map_list for all lines '''
result = list(content) # make a copy
for p in map_list:
# result = [l.replace(p[0], p[1]) for l in result] # Case-sensitive
result = [ireplace(p[0], p[1], l) for l in result]
return result
def replace_math_functions(content,math_list):
''' replaice all math functions in content '''
for p in math_list:
content = [ireplace(p[0], p[1], l) for l in content]
return content
def process_do(line):
''' replaice Fortran do to Python for:
do i=1, N => for i in range(0, N):
do j=1, M, 2 => for j in range(0, M, 2):
do iq=ip+1, N => for iq in range(ip+1, N):
'''
if line.startswith('#'):
return line
if line.strip().startswith( 'do' ):
if '#' in line:
do_var_lims,comment = line.split('#')
comment = ' #'+''.join(comment)
else:
do_var_lims,comment = line, ''
do_var,lims = do_var_lims.split('=')
for_var = do_var.replace('do','for') + ' in range('
lims=lims.split(',')
lims=[i.strip() for i in lims]
if str(lims[0])=='1': # heuristic correction for 0-based arrays
lims[0]='0' # warning: this can be unnecessery sometimes.
result = for_var + ', '.join(lims) + '):'
if comment:
result += comment
return result
else:
return line
def replace_all_do(content):
''' replaice do statements for all lines '''
result = [process_do(l) for l in content]
return result
def adjust_array(line, arr):
''' Conversion of Fortran array access to Python:
line = 'A(i,j) = A(m,A(k,l))'
arr = 'A'
result = 'A[i,j] = A[m,A[k,l]]'
'''
if line.startswith('#'):
return line
i = line.find(arr+'(')
while i >= 0:
j = line.find('(',i)
line = line[:j] + '[' + line[j+1:]
c = 1
for k in range(j+1,len(line)):
if line[k] == '(':
c += 1
if line[k] == ')':
c -= 1
if c == 0:
line = line[:k] + ']' + line[k+1:]
# i = line.find(arr+'(', k+1) # does not process nested arrays
i = line.find(arr+'(')
break
return line
def adjust_arrays(line):
''' adjust all arrays in a line '''
for a in arrays:
line = adjust_array(line, a)
return line
def adjust_all_arrays(content):
''' adjust all arrays in all lines '''
result = [adjust_arrays(l) for l in content]
return result
def adjust_functions(content):
""" Adds ':' after ')' """
for n,line in enumerate(content):
count = 0
if line.strip().startswith('def'):
i = line.find('(')
if i >= 0:
count = 1
for k in range(i,len(line)):
#print(k, line[k])
if line[k] == '#':
break
if line[k] == ')':
count = 0
content[n] = line[:k+1] + ':' + line[k+1:]
break
else:
count = 0
i = line.find('#')
if i >= 0:
content[n] = line[:i] + ':' + line[i:]
else:
content[n] = line + ':'
else:
if count > 0:
i = 0
for k in range(i,len(line)):
if line[k] == '#':
break
if line[k] == ')':
count = 0
content[n] = line[:k+1] + ':' + line[k+1:]
break
return content
def list2file(fname, output):
''' list of string to text file '''
with open(fname,'w', encoding="utf8") as out:
for line in output:
out.write(line+'\n')
def f90_to_py(content,map_list,math_list,arrays):
''' Fortran 90 to Python conversion
by string manipulations
content - input list of f90 file content strings
map_list - list of substitution pairs,
e.g. ('.lt.',' < '),('DABS','abs'),
output - list of python file content strings
'''
output = replace_statements(content,map_list)
output = replace_math_functions(output,math_list)
output = replace_all_do(output)
output = adjust_all_arrays(output)
output = adjust_functions(output)
return output
fname='ujacobi.f90'
foutname='ujacobi.py'
List of arrays
arrays=['A','D','V','B','Z']
Read Fortran file
content = file2list(fname)
Generaqte conversion
output = f90_to_py(content,map_list,math_list,arrays)
Write Python file
list2file(foutname, output)