Reading YAML file with Python results in yaml.scanner.ScannerError: mapping values are not allowed here

Question

我正在使用以下代码：

import yaml
with open('/Users/edamame/my_logins/my_config.yaml', 'r') as infile:
    db_cfg = yaml.safe_load(infile)

尝试读取 my_config.yaml:

database_info:
    username: edamame
    password: mypassword
    host: 1.2.3.4
    port: 3306
    database: mydb

但出现以下错误：

Traceback (most recent call last):
  File "/Users/edamame/my_project/extract_appointments.py", line 16, in <module>
    db_cfg = yaml.safe_load(infile)
  File "/Users/edamame/my_project/venv/lib/python3.6/site-packages/yaml/__init__.py", line 94, in safe_load
    return load(stream, SafeLoader)
  File "/Users/edamame/my_project/venv/lib/python3.6/site-packages/yaml/__init__.py", line 72, in load
    return loader.get_single_data()
  File "/Users/edamame/my_project/venv/lib/python3.6/site-packages/yaml/constructor.py", line 35, in get_single_data
    node = self.get_single_node()
  File "/Users/edamame/my_project/venv/lib/python3.6/site-packages/yaml/composer.py", line 36, in get_single_node
    document = self.compose_document()
  File "/Users/edamame/my_project/venv/lib/python3.6/site-packages/yaml/composer.py", line 55, in compose_document
    node = self.compose_node(None, None)
  File "/Users/edamame/my_project/venv/lib/python3.6/site-packages/yaml/composer.py", line 84, in compose_node
    node = self.compose_mapping_node(anchor)
  File "/Users/edamame/my_project/venv/lib/python3.6/site-packages/yaml/composer.py", line 127, in compose_mapping_node
    while not self.check_event(MappingEndEvent):
  File "/Users/edamame/my_project/venv/lib/python3.6/site-packages/yaml/parser.py", line 98, in check_event
    self.current_event = self.state()
  File "/Users/edamame/my_project/venv/lib/python3.6/site-packages/yaml/parser.py", line 428, in parse_block_mapping_key
    if self.check_token(KeyToken):
  File "/Users/edamame/my_project/venv/lib/python3.6/site-packages/yaml/scanner.py", line 116, in check_token
    self.fetch_more_tokens()
  File "/Users/edamame/my_project/venv/lib/python3.6/site-packages/yaml/scanner.py", line 220, in fetch_more_tokens
    return self.fetch_value()
  File "/Users/edamame/my_project/venv/lib/python3.6/site-packages/yaml/scanner.py", line 576, in fetch_value
    self.get_mark())
yaml.scanner.ScannerError: mapping values are not allowed here
  in "/Users/edamame/my_logins/my_config.yaml", line 5, column 9

这是我的安装：知道我在这里错过了什么吗？

Answer 1

我无法在虚拟环境中使用几乎相同的代码进行复制运行 Python 2 和 3 以及 PyYAML==3.13。

>>> import yaml
>>> with open('sample.yaml', 'r') as infile:
...   db_cfg = yaml.safe_load(infile)
... 
>>> db_cfg
{'database_info': {'username': 'edamame', 'password': 'mypassword', 'host': '1.2.3.4', 'port': 3306, 'database': 'mydb'}}

您是否在使用与示例完全相同的输入时遇到此错误？

否则，请确保您的输入格式正确。每个冒号后是否有 space？缩进是否正确？

Answer 2

您显示的输入不会产生该错误。你可以试试 here:

您很可能有一些空白差异，很可能在 port: 3306 行中。请注意，因为 PyYAML 早于最新的 YAML 标准（2009 年的 1.2）它仍然将一些 Unicode 空白字符视为空白，尽管标准没有。

如果您无法通过查看文件找到导致此问题的原因，则有两种可能的选择：

尝试一次一行地将文件复制并粘贴到在线解析器中，直到看到错误弹出。这让您清楚地知道哪条线是错误的。
使用 YAML 转储程序从 Python

后者在 PyYAML 中不容易完成，因为它会在写入时对映射的键进行排序。

import sys
import ruamel.yaml
from ruamel.yaml.comments import CommentedMap as cm

data = cm()
data['database_info'] = d = cm()
d['username'] = 'edamame'
d['password'] = 'mypassword'
d['host'] = '1.2.3.4'
d['port'] = 3306
d['database'] = 'mydb'


yaml = ruamel.yaml.YAML()
yaml.indent(mapping=4)

with open('my_config.yaml', 'w') as ofp:
    yaml.dump(data, ofp)

在my_config.yaml中生成以下内容：

database_info:
    username: edamame
    password: mypassword
    host: 1.2.3.4
    port: 3306
    database: mydb

（甚至）PyYAML 应该能够读取的文件。

Reading YAML file with Python results in yaml.scanner.ScannerError: mapping values are not allowed here

Reading YAML file with Python results in yaml.scanner.ScannerError: mapping values are not allowed here

python

yaml

pyyaml