如何使用 python 向 yaml 文件添加新行/更新数据？

Question

I want to update my.yaml file and in each iteration new data added to my.yaml file while previous data is still saved, here is piece of my code:

import yaml

num=0
for i in range(4):
    num +=1    
    data_yaml =[{"name" : num,  "point" : [x, y , z]}]

    with open('points.yaml', 'w') as yaml_file:
        yaml.dump(data_yaml, yaml_file)  

and this is my target output result which I want to achieve in my points.yaml file:

- name: 1
  point: [0.7, -0.2, 0.22]
- name: 2
  point: [0.6, -0.11, 0.8]
- name: 3
  point: [0.4, -0.2, 0.6]
- name: 4
  point: [0.3, -0.7, 0.8]
- name: 5
  point: [0.1, -0.4, 0.2]

How to append or add automatically new lines beside previous data in.yaml file?

Answer 1

In the expected output your root level data structure is a sequence. In your Python program you should therefor start with an empty list. (In case you didn't know that, the easiest thing to do is .load the YAML document that you hand-crafted and see how it ends up as data structure Python.)

Not only do you seem to be using a version of Python that is EOL, but also old (compatibility) routines for ruamel.yaml. If you cannot change the former, at least start using the new ruamel.yaml API:

from __future__ import print_function

import sys
import ruamel.yaml

points = [
  [0.7, -0.2, 0.22],
  [0.6, -0.11, 0.8],
  [0.4, -0.2, 0.6],
  [0.3, -0.7, 0.8],
  [0.1, -0.4, 0.2],
]

data = []

yaml = ruamel.yaml.YAML(typ='safe')

num=0
for i in range(5):
    num +=1
    x, y, z = points[i]
    data.append({"name" : num,
    "point" : [x, y , z ]
    })

    with open('points.yaml', 'w') as yaml_file:
         yaml.dump(data, yaml_file)

with open('points.yaml') as yaml_file:
    print(yaml_file.read())

which gives:

- name: 1
  point: [0.7, -0.2, 0.22]
- name: 2
  point: [0.6, -0.11, 0.8]
- name: 3
  point: [0.4, -0.2, 0.6]
- name: 4
  point: [0.3, -0.7, 0.8]
- name: 5
  point: [0.1, -0.4, 0.2]

Please note that I changed the argument to range() to 5.