There is a Fortran code snippets thread. I am starting one here for small scripts related to scientific programming. The Python script below (also here)
#!/usr/bin/env python3
“”"
Convert readable scientific notation in a text file to fixed decimal notation.
Default rule:
convert x if 1e-4 <= abs(x) < 1e6
Examples:
1.00000E+00 → 1.00000
-3.12042E-01 → -0.312042
1.42550E-04 → 0.000142550
8.24236E-05 → kept by default
Usage:
python xscientific_notation_to_fixed.py input.txt
python xscientific_notation_to_fixed.py input.txt output.txt
python xscientific_notation_to_fixed.py input.txt output.txt --fixed-min 1e-6
python xscientific_notation_to_fixed.py input.txt output.txt --fixed-min 0 --fixed-max 1e4
“”"
import argparse
import re
from decimal import Decimal, InvalidOperation
SCI_RE = re.compile(
r"“”
(?<![A-Za-z0-9_.])
[±]?
(?:
(?:\d+.\d*) |
(?:.\d+) |
(?:\d+)
)
[Ee]
[±]?
\d+
(?![A-Za-z0-9_.])
“”",
re.VERBOSE,
)
def decimal_arg(s):
“”“Parse a command-line argument as Decimal.”“”
try:
x = Decimal(s)
except InvalidOperation as exc:
raise argparse.ArgumentTypeError(f"invalid decimal value: {s}") from exc
if x < 0:
raise argparse.ArgumentTypeError("value must be nonnegative")
return x
def fixed_decimal_string(s):
“”“Return the fixed-point decimal representation of a scientific number.”“”
try:
x = Decimal(s)
except InvalidOperation:
return s
out = format(x, "f")
# Avoid "-0.0000" style output.
if Decimal(out) == 0:
out = out.lstrip("-")
return out
def should_convert(
s,
fixed_min=Decimal(“1e-4”),
fixed_max=Decimal(“1e6”),
max_fixed_len=12,
max_leading_frac_zeros=3,
):
“”"
Decide whether fixed notation is more readable.
Convert only when:
fixed_min <= abs(x) < fixed_max
Also avoid converting when fixed notation is visually too long.
"""
try:
x = Decimal(s)
except InvalidOperation:
return False
ax = abs(x)
if ax == 0:
return True
if ax < fixed_min:
return False
if ax >= fixed_max:
return False
fixed = fixed_decimal_string(s)
tmp = fixed.lstrip("+-")
# Count leading zeros after the decimal point.
leading_frac_zeros = 0
if tmp.startswith("0."):
frac = tmp[2:]
for ch in frac:
if ch == "0":
leading_frac_zeros += 1
else:
break
if leading_frac_zeros > max_leading_frac_zeros:
return False
# Ignore sign when judging visual length.
if len(tmp) > max_fixed_len:
return False
return True
def convert_text(
text,
fixed_min=Decimal(“1e-4”),
fixed_max=Decimal(“1e6”),
max_fixed_len=12,
max_leading_frac_zeros=3,
):
def convert_match(match):
s = match.group(0)
if not should_convert(
s,
fixed_min=fixed_min,
fixed_max=fixed_max,
max_fixed_len=max_fixed_len,
max_leading_frac_zeros=max_leading_frac_zeros,
):
return s
return fixed_decimal_string(s)
return SCI_RE.sub(convert_match, text)
def main():
parser = argparse.ArgumentParser(
description=“Convert selected scientific notation values to fixed notation.”
)
parser.add_argument("input", help="input text file")
parser.add_argument("output", nargs="?", help="output text file")
parser.add_argument(
"--fixed-min",
type=decimal_arg,
default=Decimal("1e-4"),
help="smallest absolute value to convert to fixed notation; default: 1e-4",
)
parser.add_argument(
"--fixed-max",
type=decimal_arg,
default=Decimal("1e6"),
help="largest absolute value to convert to fixed notation; default: 1e6",
)
parser.add_argument(
"--max-fixed-len",
type=int,
default=12,
help="maximum length of fixed representation, excluding sign; default: 12",
)
parser.add_argument(
"--max-leading-frac-zeros",
type=int,
default=3,
help=(
"maximum allowed leading zeros after decimal point before first "
"nonzero digit; default: 3"
),
)
args = parser.parse_args()
if args.fixed_min >= args.fixed_max:
raise SystemExit("--fixed-min must be less than --fixed-max")
with open(args.input, "r", encoding="utf-8") as f:
text = f.read()
converted = convert_text(
text,
fixed_min=args.fixed_min,
fixed_max=args.fixed_max,
max_fixed_len=args.max_fixed_len,
max_leading_frac_zeros=args.max_leading_frac_zeros,
)
if args.output:
with open(args.output, "w", encoding="utf-8", newline="") as f:
f.write(converted)
else:
print(converted, end="")
if name == “main”:
main()
converts numbers in scientific notation to fixed notation when doing so makes the output more readable, converting for example
AR coefficient matrix
[,1] [,2]
[1,] -2.62080E-01 -7.17269E-01
[2,] 2.40473E-01 8.52959E-01
MA coefficient matrix
[,1] [,2]
[1,] 1.60933E-01 7.26566E-01
[2,] -1.95728E-01 -8.80067E-01
to
AR coefficient matrix
[,1] [,2]
[1,] -0.262080 -0.717269
[2,] 0.240473 0.852959
MA coefficient matrix
[,1] [,2]
[1,] 0.160933 0.726566
[2,] -0.195728 -0.880067
You could adjust the format strings in the Fortran code, but sometimes it is more convenient to post-process results.
