gnuradio error: found character '%' that cannot start any token

Question

我在运行 GNU Radio Companion 时遇到此错误。当然，multi_rtl_source.block.yml 块不起作用，也不会出现在菜单中：

    ERROR:gnuradio.grc.core.platform:Error while loading /usr/local/share/gnuradio/grc/blocks/multi_rtl_source.block.yml
Traceback (most recent call last):
  File "/usr/lib/python3.8/site-packages/gnuradio/grc/core/platform.py", line 169, in build_library
    data = cache.get_or_load(file_path)
  File "/usr/lib/python3.8/site-packages/gnuradio/grc/core/cache.py", line 66, in get_or_load
    data = yaml.safe_load(fp)
  File "/usr/lib/python3.8/site-packages/yaml/__init__.py", line 162, in safe_load
    return load(stream, SafeLoader)
  File "/usr/lib/python3.8/site-packages/yaml/__init__.py", line 114, in load
    return loader.get_single_data()
  File "/usr/lib/python3.8/site-packages/yaml/constructor.py", line 49, in get_single_data
    node = self.get_single_node()
  File "/usr/lib/python3.8/site-packages/yaml/composer.py", line 36, in get_single_node
    document = self.compose_document()
  File "/usr/lib/python3.8/site-packages/yaml/composer.py", line 55, in compose_document
    node = self.compose_node(None, None)
  File "/usr/lib/python3.8/site-packages/yaml/composer.py", line 84, in compose_node
    node = self.compose_mapping_node(anchor)
  File "/usr/lib/python3.8/site-packages/yaml/composer.py", line 133, in compose_mapping_node
    item_value = self.compose_node(node, item_key)
  File "/usr/lib/python3.8/site-packages/yaml/composer.py", line 82, in compose_node
    node = self.compose_sequence_node(anchor)
  File "/usr/lib/python3.8/site-packages/yaml/composer.py", line 111, in compose_sequence_node
    node.value.append(self.compose_node(node, index))
  File "/usr/lib/python3.8/site-packages/yaml/composer.py", line 84, in compose_node
    node = self.compose_mapping_node(anchor)
  File "/usr/lib/python3.8/site-packages/yaml/composer.py", line 127, in compose_mapping_node
    while not self.check_event(MappingEndEvent):
  File "/usr/lib/python3.8/site-packages/yaml/parser.py", line 98, in check_event
    self.current_event = self.state()
  File "/usr/lib/python3.8/site-packages/yaml/parser.py", line 428, in parse_block_mapping_key
    if self.check_token(KeyToken):
  File "/usr/lib/python3.8/site-packages/yaml/scanner.py", line 116, in check_token
    self.fetch_more_tokens()
  File "/usr/lib/python3.8/site-packages/yaml/scanner.py", line 258, in fetch_more_tokens
    raise ScannerError("while scanning for the next token", None,
yaml.scanner.ScannerError: while scanning for the next token
found character '%' that cannot start any token
  in "/usr/local/share/gnuradio/grc/blocks/multi_rtl_source.block.yml", line 33, column 5
ERROR:gnuradio.grc.core.platform:while scanning for the next token
found character '%' that cannot start any token
  in "/usr/local/share/gnuradio/grc/blocks/multi_rtl_source.block.yml", line 33, column 5
Traceback (most recent call last):
  File "/usr/lib/python3.8/site-packages/gnuradio/grc/core/platform.py", line 169, in build_library
    data = cache.get_or_load(file_path)
  File "/usr/lib/python3.8/site-packages/gnuradio/grc/core/cache.py", line 66, in get_or_load
    data = yaml.safe_load(fp)
  File "/usr/lib/python3.8/site-packages/yaml/__init__.py", line 162, in safe_load
    return load(stream, SafeLoader)
  File "/usr/lib/python3.8/site-packages/yaml/__init__.py", line 114, in load
    return loader.get_single_data()
  File "/usr/lib/python3.8/site-packages/yaml/constructor.py", line 49, in get_single_data
    node = self.get_single_node()
  File "/usr/lib/python3.8/site-packages/yaml/composer.py", line 36, in get_single_node
    document = self.compose_document()
  File "/usr/lib/python3.8/site-packages/yaml/composer.py", line 55, in compose_document
    node = self.compose_node(None, None)
  File "/usr/lib/python3.8/site-packages/yaml/composer.py", line 84, in compose_node
    node = self.compose_mapping_node(anchor)
  File "/usr/lib/python3.8/site-packages/yaml/composer.py", line 133, in compose_mapping_node
    item_value = self.compose_node(node, item_key)
  File "/usr/lib/python3.8/site-packages/yaml/composer.py", line 82, in compose_node
    node = self.compose_sequence_node(anchor)
  File "/usr/lib/python3.8/site-packages/yaml/composer.py", line 111, in compose_sequence_node
    node.value.append(self.compose_node(node, index))
  File "/usr/lib/python3.8/site-packages/yaml/composer.py", line 84, in compose_node
    node = self.compose_mapping_node(anchor)
  File "/usr/lib/python3.8/site-packages/yaml/composer.py", line 127, in compose_mapping_node
    while not self.check_event(MappingEndEvent):
  File "/usr/lib/python3.8/site-packages/yaml/parser.py", line 98, in check_event
    self.current_event = self.state()
  File "/usr/lib/python3.8/site-packages/yaml/parser.py", line 428, in parse_block_mapping_key
    if self.check_token(KeyToken):
  File "/usr/lib/python3.8/site-packages/yaml/scanner.py", line 116, in check_token
    self.fetch_more_tokens()
  File "/usr/lib/python3.8/site-packages/yaml/scanner.py", line 258, in fetch_more_tokens
    raise ScannerError("while scanning for the next token", None,
yaml.scanner.ScannerError: while scanning for the next token
found character '%' that cannot start any token
  in "/usr/local/share/gnuradio/grc/blocks/multi_rtl_source.block.yml", line 33, column 5

我也明白了：

>>> Check: /usr/local/share/gnuradio/grc/blocks/multi_rtl_source.block.yml
>>> FlowGraph Error: while scanning for the next token
found character '%' that cannot start any token
  in "/usr/local/share/gnuradio/grc/blocks/multi_rtl_source.block.yml", line 33, column 5

第 33 行第 5 列有一个 YAML 指令：

-   id: sync_gain0
    label: Ch0: Sync RF Gain (dB)
    category: Synchronization
    dtype: real
    default: 10
    hide: \
    %if nchan() > n: <== line 33
part
    %else:
all
   %endif

可以找到 multi_rtl_source.block.yml 的完整代码 here

在 GNU Radio wiki 中有一个 article，其中写道您可以将 YAML dicrices 放在 GRC 块中。那么这个错误是从哪里来的以及如何修复它？

Answer 1

    hide: \

在 YAML 中，获得多行字符串的正确方法是使用 > 或 | 说明符（参见 https://yaml-multiline.info/）而不是 \，例如

    hide: |

或者你可以像这样在一行中写隐藏条件

    hide: ${'part' if nchan > 0 else 'all'}

这是 gen_multi_rtl_block.py

中的修复方法

@@ -104,57 +100,32 @@ template_p = """\
     category: Synchronization
     dtype: real
     default: 10
-    hide: &
-    ${"%"} if nchan() > n:
-part
-    ${"%"} else:
-all
-    ${"%"} endif
+    hide: ${'$'}{'part' if nchan > ${n} else 'all'}

gnuradio error: found character '%' that cannot start any token

gnuradio error: found character '%' that cannot start any token

yaml

gnuradio

gnuradio-companion