Documentation of the RequestArgument class.
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2 changed files with 159 additions and 6 deletions
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@ -1,121 +1,273 @@
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from typing import List, Optional, Tuple, Union
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from typing import Iterator, List, Optional, Tuple, Union
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class RequestArgument(object):
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"""
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Container class for HTTP request arguments that simplifies dealing with
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- scalar and array arguments:
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Automatically converts between single values and arrays where necessary: Arrays with one element can be
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accessed as scalars, and scalars can be iterated, yielding themselves as a single item.
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- UTF-8 strings and binary data (e.g. file uploads):
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All data can be retrieved both as a str (if utf-8 decoding is possible) and a bytes object.
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The objects returned from iteration or indexing are immutable views of (parts of) this object.
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Usage example:
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qsargs = urllib.parse.parse_qs(qs, strict_parsing=True, keep_blank_values=True, errors='strict')
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args: Dict[str, RequestArgument] = dict()
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for k, vs in qsargs:
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args[k] = RequestArgument(k)
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for v in vs:
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# text/plain usually is a sensible choice for values decoded from urlencoded strings
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# IF ALREADY IN STRING FORM (which parse_qs does)!
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args[k].append('text/plain', v)
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if 'username' in args and args['username'].is_scalar:
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username: str = args['username'].get_str()
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else:
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raise ValueError()
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"""
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def __init__(self,
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name: str,
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value: Union[Tuple[str, Union[bytes, str]], List[Tuple[str, Union[bytes, str]]]] = None) -> None:
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"""
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Create a new RequestArgument with a name and optionally an initial value.
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:param name: The name for this argument, as provided via GET or POST.
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:param value: The initial value, if any. Optional, initializes with empty array if omitted.
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"""
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# Assign name
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self.__name: str = name
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# Initialize value
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self.__value: Union[Tuple[str, Union[bytes, str]], List[Tuple[str, Union[bytes, str]]]] = None
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# Default to empty array
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if value is None:
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self.__value = []
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else:
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if isinstance(value, list):
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if len(value) == 1:
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# An array of length 1 will be reduced to a scalar
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self.__value = value[0]
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else:
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# Store the array
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self.__value = value
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else:
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# Scalar value, simply store
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self.__value = value
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@property
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def is_array(self) -> bool:
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"""
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:return: True, if the value is a (possibly empty) array, False otherwise.
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"""
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return isinstance(self.__value, list)
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@property
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def is_scalar(self) -> bool:
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"""
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:return: True, if the value is a single scalar value, False otherwise.
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"""
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return not isinstance(self.__value, list)
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@property
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def is_view(self) -> bool:
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"""
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:return: True, if this instance is an immutable view, False otherwise.
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"""
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return False
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@property
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def name(self) -> str:
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"""
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:return: The name of this argument.
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"""
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return self.__name
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def get_str(self, index: int = None) -> Optional[str]:
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def get_str(self, index: int = None) -> str:
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"""
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Attempts to return a value as a string. If this instance is an scalar, no index must be provided. If this
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instance is an array, an index must be provided.
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:param index: For array values: The index of the value to retrieve. For scalar values: None (default).
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:return: An UTF-8 string representation of the requested value.
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:raises UnicodeDecodeError: If the value cannot be decoded into an UTF-8 string.
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:raises IndexError: If the index is out of bounds.
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:raises ValueError: If this is an array value, and no index is provided, or if this is a scalar value and an
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index is provided.
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"""
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if self.is_array:
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# instance is an array value
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if index is None:
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# Needs an index for array values
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raise ValueError('index must not be None')
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# Type hint; access array element
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v: Tuple[str, Union[bytes, str]] = self.__value[index]
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if isinstance(v[1], str):
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# The value already is a string, return
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return v[1]
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elif isinstance(v[1], bytes):
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# The value is a bytes object, attempt to decode
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return v[1].decode('utf-8')
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else:
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# instance is a scalar value
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if index is not None:
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# Must not have an index for array values
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raise ValueError('index must be None')
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if isinstance(self.__value[1], str):
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# The value already is a string, return
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return self.__value[1]
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elif isinstance(self.__value[1], bytes):
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# The value is a bytes object, attempt to decode
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return self.__value[1].decode('utf-8')
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def get_bytes(self, index: int = None) -> Optional[bytes]:
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def get_bytes(self, index: int = None) -> bytes:
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"""
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Attempts to return a value as a bytes object. If this instance is an scalar, no index must be provided. If
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this instance is an array, an index must be provided.
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:param index: For array values: The index of the value to retrieve. For scalar values: None (default).
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:return: A bytes object representation of the requested value. Strings will be encoded as UTF-8.
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:raises IndexError: If the index is out of bounds.
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:raises ValueError: If this is an array value, and no index is provided, or if this is a scalar value and an
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index is provided.
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"""
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if self.is_array:
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# instance is an array value
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if index is None:
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# Needs an index for array values
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raise ValueError('index must not be None')
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# Type hint; access array element
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v: Tuple[str, Union[bytes, str]] = self.__value[index]
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if isinstance(v[1], bytes):
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# The value already is a bytes object, return
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return v[1]
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elif isinstance(v[1], str):
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# The value is a string, encode first
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return v[1].encode('utf-8')
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else:
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# instance is a scalar value
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if index is not None:
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# Must not have an index for array values
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raise ValueError('index must be None')
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if isinstance(self.__value[1], bytes):
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# The value already is a bytes object, return
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return self.__value[1]
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elif isinstance(self.__value[1], str):
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# The value is a string, encode first
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return self.__value[1].encode('utf-8')
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def get_content_type(self, index: int = None) -> Optional[str]:
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"""
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Attempts to retrieve a value's Content-Type. If this instance is an scalar, no index must be provided. If this
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instance is an array, an index must be provided.
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:param index: For array values: The index of the value to retrieve. For scalar values: None (default).
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:return: The Content-Type of the requested value, as sent by the client. Not necessarily trustworthy.
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:raises IndexError: If the index is out of bounds.
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:raises ValueError: If this is an array value, and no index is provided, or if this is a scalar value and an
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index is provided.
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"""
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if self.is_array:
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# instance is an array value
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if index is None:
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# Needs an index for array values
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raise ValueError('index must not be None')
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# Type hint; access array element
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v: Tuple[str, Union[bytes, str]] = self.__value[index]
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# Return the content type of the requested value
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return v[0]
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else:
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# instance is a scalar value
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if index is not None:
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# Must not have an index for array values
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raise ValueError('index must be None')
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# Return the content type of the scalar value
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return self.__value[0]
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def append(self, ctype: str, value: Union[str, bytes]):
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"""
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Append a value to this instance. Turns an empty argument into a scalar and a scalar into an array.
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:param ctype: The Content-Type, as provided in the request.
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:param value: The scalar value to append, either a string or bytes object.
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:raises TypeError: If called on an immutable view.
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"""
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if self.is_view:
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# This is an immutable view, raise exception
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raise TypeError('A RequestArgument view is immutable!')
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if len(self) == 0:
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# Turn an empty argument into a scalar
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self.__value = ctype, value
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else:
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# First turn the scalar into a one-element array ...
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if self.is_scalar:
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self.__value = [self.__value]
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# ... then append the new value
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self.__value.append((ctype, value))
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def __len__(self):
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def __len__(self) -> int:
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"""
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:return: Number of values for this argument.
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"""
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return len(self.__value) if self.is_array else 1
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def __iter__(self):
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def __iter__(self) -> Iterator['RequestArgument']:
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"""
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Iterate the values of this argument. Each value is accessible as if it were a scalar RequestArgument in turn,
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although they are immutable.
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:return: An iterator that yields immutable views of the values.
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"""
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if self.is_scalar:
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# If this is a scalar, yield an immutable view of the single value
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yield _View(self.__name, self.__value)
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else:
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# Typing helper
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_value: List[Tuple[str, Union[bytes, str]]] = self.__value
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for v in _value:
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# If this is an array, yield an immutable scalar view for each (ctype, value) element in the array
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yield _View(self.__name, v)
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def __getitem__(self, index: Union[int, slice]):
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"""
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Index the argument with either an int or a slice. The returned values are represented as immutable
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RequestArgument views. Scalar arguments may be indexed with int(0).
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:param index: The index or slice.
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:return: An immutable view of the indexed elements of this argument.
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"""
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if self.is_scalar:
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# Scalars may only be indexed with 0
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if index == 0:
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# Return an immutable view of the single scalar value
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return _View(self.__name, self.__value)
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raise ValueError('Scalar RequestArgument only indexable with 0')
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# Pass the index or slice through to the array, packing the result in an immutable view
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return _View(self.__name, self.__value[index])
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class _View(RequestArgument):
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"""
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This class represents an immutable view of a (subset of a) RequestArgument object. Should not be instantiated
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directly.
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"""
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def __init__(self, name: str, value: Union[Tuple[str, Union[bytes, str]], List[Tuple[str, Union[bytes, str]]]]):
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def __init__(self, name: str, value: Union[Tuple[str, Union[bytes, str]], List[Tuple[str, Union[bytes, str]]]])\
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-> None:
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"""
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Create a new immutable view of a (subset of a) RequestArgument.
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:param name: The name for this argument, same as in the original RequestArgument.
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:param value: The values to represent in this view, obtained by e.g. indexing or slicing.
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"""
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super().__init__(name, value)
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@property
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def is_view(self) -> bool:
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"""
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:return: True, if this instance is an immutable view, False otherwise.
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"""
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return True
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@ -69,6 +69,7 @@ def _parse_multipart(body: bytes, boundary: str) -> List[RequestArgument]:
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args[name] = RequestArgument(name)
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args[name].append(hdr['Content-Type'].strip(), part)
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if not has_name:
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# Content-Disposition header without name attribute
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raise ValueError('mutlipart/form-data part without name attribute')
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return list(args.values())
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