Using Inline Yaml Formatting over multiple lines? - dictionary

Question

I'm trying to create a YAML file for use with nose-testconfig with data like this:
"Computers":
"Brand: "Dell"
"Cost": 500
"IP": "194.66.82.11"
"Brand: "HP"
"Cost": 600
"IP": "194.66.82.13"
"Brand: "Asus"
"Cost": 550
"IP": "194.66.82.15"
The problem I'm having is that each of the repeated items just get overwritten. I need to have it be a list of lists of dictionaries, however I don't know how to make that work. I can't just use the inline formatting with brackets and braces because the actual data I'm working with has a lot more data in each dictionary, so the lines would be way too long.
Is there a way to format this in a way that keeps each list of dictionaries separate?

Answer 1

What I think you want is this:
Computers:
- Brand: Dell
Cost: 500
IP: 194.66.82.11
- Brand: HP
Cost: 600
IP: 194.66.82.13
- Brand: Asus
Cost: 550
IP: 194.66.82.15
This represents a mapping ("dictionary") with one key, "Computers," whose value is a sequence ("list") having three items, each of which is a mapping with the three keys "Brand," "Cost", and "IP."
In JavaScript, for example, it would deserialize to this structure:
{ Computers:
[ { Brand: "Dell",
Cost: 500,
IP: "192.66.82.11"
},
{ Brand: "HP",
Cost: 600,
IP: "192.168.82.13"
},
{ Brand: "Asus",
Cost: 550,
IP: "192.168.82.15"
}
]
}
P.S. You'll notice I removed the quotation marks. Quotation marks are an antipattern in YAML—there are very few situations where they're necessary (for example, if you wanted "500" to be deserialized as a string instead of a number) and they add a lot of line noise, defeating the purpose of YAML, which is ease of reading and editing.
P.P.S. A utility I find hugely useful is this Online YAML Parser, which will show you the result, in either JSON or Python notation, of any YAML input as you type.

Answer 2

What you should do if you are unsure about how your YAML for a certain construct should look is create the construction in your programming language of choice (for which there should be no such uncertainty), and then dump it. E.g. in Python:
import sys
import ruamel.yaml
data = dict(Computers=[
dict(Brand="Dell", Cost=500, IP="194.66.82.11"),
dict(Brand="HP", Cost=600, IP="194.66.82.13"),
dict(Brand="Asus", Cost=550, IP="194.66.82.15"),
])
yaml = YAML()
yaml.dump(data, sys.stdout)
gives you:
Computers:
- IP: 194.66.82.11
Brand: Dell
Cost: 500
- IP: 194.66.82.13
Brand: HP
Cost: 600
- IP: 194.66.82.15
Brand: Asus
Cost: 550
What you see is that quotes around simple scalars are unnecessary (but they are allowed according to the specification, so it is perfectly OK to put them in). You also see that you missed putting a list in your YAML file (which in block mode is indicated by the - dashed items).
Using this way it is easy to determine for yourself how your data should be formatted to be valid YAML. For some parsers you need to try with block or non-flow style formatting to get a better readable result, for ruamel.yaml (of which I am the author) block style is default as it is, IMO, more readable.
Please note that keys for mappings in YAML are by definition unordered, although ruamel.yaml can preserve these for you in roundtrip mode