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Support !degree & !randians yaml prefixes #7

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Support !degree & !randians yaml prefixes #7

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cddd14f
Support !degree & !randians yaml prefixes
JafarAbdi Feb 18, 2023
6c61e6e
Update launch_param_builder/utils.py
JafarAbdi Feb 27, 2023
49a106d
Update launch_param_builder/utils.py
JafarAbdi Feb 27, 2023
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27 changes: 24 additions & 3 deletions launch_param_builder/utils.py
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@
from typing import List, Union
import xacro
from ament_index_python.packages import get_package_share_directory
import math


class ParameterBuilderFileNotFoundError(KeyError):
Expand All @@ -52,6 +53,20 @@ class ParameterBuilderFileNotFoundError(KeyError):
]


def construct_angle_radians(loader, node):
"""Utility function to construct radian values from yaml."""
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value = loader.construct_scalar(node)
try:
return float(value)
except SyntaxError:
raise Exception(f"invalid expression: {value}")


def construct_angle_degrees(loader, node):
"""Utility function for converting degrees into radians from yaml."""
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return math.radians(construct_angle_radians(loader, node))


def raise_if_file_not_found(file_path: Path):
if not file_path.exists():
raise ParameterBuilderFileNotFoundError(f"File {file_path} doesn't exist")
Expand All @@ -62,17 +77,23 @@ def load_file(file_path: Path):
try:
with open(file_path, "r") as file:
return file.read()
except EnvironmentError: # parent of IOError, OSError *and* WindowsError where available
except OSError: # parent of IOError, OSError *and* WindowsError where available
return None


def load_yaml(file_path: Path):
raise_if_file_not_found(file_path)

try:
yaml.SafeLoader.add_constructor("!radians", construct_angle_radians)
yaml.SafeLoader.add_constructor("!degrees", construct_angle_degrees)
except Exception:
raise Exception("yaml support not available; install python-yaml")

try:
with open(file_path, "r") as file:
return yaml.load(file, Loader=yaml.FullLoader)
except EnvironmentError: # parent of IOError, OSError *and* WindowsError where available
return yaml.safe_load(file)
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@sea-bass sea-bass Feb 27, 2023 •
edited
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Based on this resource and some limitation I found when integrating this in Studio, I have a suggestion.

First, make a function like this which we can use standalone:

def get_yaml_loader():
    """Gets a YAML loader that additionally supports custom constructors."""
    loader = yaml.SafeLoader
    loader.add_constructor("!radians", construct_angle_radians)
    loader.add_constructor("!degrees", construct_angle_degrees)
    return loader

Then, in your implementation, you can do:

def load_yaml(file_path: Path, loader=get_yaml_loader()):
    ...
    return yaml.load(file, Loader=loader)

except OSError: # parent of IOError, OSError *and* WindowsError where available
return None


Expand Down