Migrate radproc from Python 2 to Python 3 with support to ArcGIS Pro

[jkreklow]

Overview:
Migrate the entire codebase of radproc from Python 2 to modern Python 3 (>=3.8 recommended). This will ensure ongoing support, compatibility with widely used libraries (numpy, pandas, etc), and improved maintainability.

Migration Tasks

• Update setup.py to support Python 3 only (add python_requires, modernize classifiers)
• Remove all from __future__ import division, print_function statements (now default in Python 3)
• Review and update all iteration methods (e.g. .iteritems(), .itervalues(), .iterkeys() → .items(), .values(), .keys())
• Replace any basestring/unicode with str and check string/byte conversions ("u''" → no longer needed)
• Verify and update file I/O for bytes/str issues, especially in binary/gzip/tar/HDF5 reads
• Ensure all usage of print functions are Python 3 compatible print()
• Update any exceptions for new syntax (except Exception as e: vs except Exception, e:)
• Remove/update any other obsolete Python 2 idioms
• Confirm all dependencies support Python 3 and update requirements.txt if needed
• Migrate GIS workflow from ArcMap arcpy syntax to ArcGIS Pro arcpy
• Run all unit/integration tests under Python 3.8+ and fix incompatibilities
• Update documentation (README, docstrings, etc.) to reflect Python 3 as required

Examples of Code Updates:

Update classifiers and python_requires in setup.py:

# Replace Python 2 classifiers: 
# 'Programming Language ::  Python :: 2',
# 'Programming Language :: Python :: 2.7',
# With Python 3 classifiers, and add python_requires:
setup(
    ...
    python_requires='>=3.8',
    classifiers=[
        'Programming Language :: Python :: 3',
        'Programming Language :: Python :: 3.8',
        'Programming Language :: Python :: 3.9',
        'Programming Language :: Python :: 3.10',
        ...
    ],
    ... 
)

Remove future imports:

# Remove these imports:
from __future__ import division, print_function

Update dictionary iteration:

# Python 2 style:
# for k, v in d. iteritems():
# Python 3 style:
for k, v in d.items():

Print function:

# Python 2:
# print "Hello"
# Python 3:
print("Hello")

String/byte distinction:

# Python 3 requires explicit encoding/decoding: 
with open(filename, 'rb') as f:
    content = f.read().decode('utf-8')

Type checks:

# Python 2:
# isinstance(s, basestring)
# Python 3:
isinstance(s, str)

Optional improvements:

• Add type hints and use f-strings for formatting
• Use pathlib.Path for file operations instead of string paths

Acceptance criteria:

• All core features pass under modern Python 3 (3.8+)
• CI pipeline for Python 3 is green (if available)
• Python 2 compatibility is dropped and no longer advertised

References:

• Porting Python 2 Code to Python 3

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