Python Naming Conventions for Dictionaries/Maps/Hashes

While other questions have tackled the broader category of sequences and modules, I ask this very specific question:

"What naming convention do you use for dictionaries and why?"

Some naming convention samples I have been considering:

# 'value' is the data type stored in the map, while 'key' is the type of key
value_for_key={key1:value1, key2,value2}
value_key={key1:value1, key2,value2}
v_value_k_key={key1:value1, key2,value2}

Don't bother answering the 'why' with "because my work tells me to", not very helpful. The reason driving the choice is more important. Are there any other good considerations for a dictionary naming convention aside from readability?

EDIT:

Chosen answer: value_key_map

Reason for chosen answer: Allows a code reviewer to quickly and easily figure out the key and value for a map, and the fact that it is a map without looking anywhere else.

key_to_value, for example surname_to_salary may be useful when there are closely interrelated maps in code: a to b, b to a, c to b etc.

I never seem to name them anything like what you proposed (i.e. keeping one way). It just seems to be much more clear when I can find a "proper name" for the hash. It might be "person_details" or "file_sizes" or "album_tracks" etc. (although the last 2 seem to have key_value names, first one a bit less). In rare cases, it will be key_value_map, or value_key_map if it's important that it's a map.

I would never assume any naming scheme for that. Sometimes the values are what you're after, sometimes the keys. My preference is "a natural name".

values_by_key

1. it is not so confusing as value_key_map: you can't confuse what is value name and what is key name
2. it doesn't name the type directly -- python style naming