无法从Ruamel.yaml导入YAML

Question

I am trying to use ruamel.yaml and am using this code straight from the ruamel's documentation but I get the error:

Traceback (most recent call last): File "ruameltest.py", line 12, in yaml = YAML() NameError: name 'YAML' is not defined

I am using Linux (RHEL)

Python 3.4.9

rpm package: python34-ruamel-yaml-0.13.14-1.el7.x86_64

How could I fix this issue?

import sys
from ruamel.yaml import YAML

inp = """\
# example
name:
  # details
  family: Smith   # very common
  given: Alice    # one of the siblings
"""

yaml = YAML()
code = yaml.load(inp)
code['name']['given'] = 'Bob'

yaml.dump(code, sys.stdout)

Answer 1

Your system installed ruamel.yaml version is severely outdated, it is now (May 2019) at 0.15.96. The API that introduced the YAML class, that your program can't find was introduced two years ago.

Additionally your Python (3.4) has been end-of-life since 2019-03-18.

You can either follow the old, PyYAML, API:

import sys
from ruamel.yaml import RoundTripLoader, RoundTripDumper, load, dump

inp = """\
# example
name:
  # details
  family: Smith   # very common
  given: Alice    # one of the siblings
"""

data = load(inp, Loader=RoundTripLoader)
data['name']['given'] = 'Bob'
dump(data, sys.stdout, Dumper=RoundTripDumper)

which gives:

# example
name:
  # details
  family: Smith   # very common
  given: Bob      # one of the siblings

Please note that you load data from YAML not code .

It would of course be better to use an up-to-date version of ruamel.yaml and a maintained version of Python. If you cannot install a newer Python version, or compile it yourself, you still can install a newer version of ruamel.yaml :

$ python3 -m venv ~/venv/yamltest
$ source ~/venv/yamltest/bin/activate
$ pip install -U pip
$ pip install 'ruamel.yaml<=0.15.94'

And then you should be able to use your program as is.

newer versions, released after 0.15.94, do not include .whl files for Python 3.4, those versions will probably still work, but you might need to have a compiler installed to make use of the C extensions, and if you do you should just download and install Python 3.7