Getting data more easily - list and dataframe

It is quite difficult to know how to get easily the data as it is different if it is an int, a float, a list or a dict.

Solution:

We created the method: get_value()

see commit ad2a27efc6edef8288e58d43fa6fe8fd95b90739

return the value of the quantity according the type of the value in order to be able to use it easily in print and plot methods: int -> int float -> float list -> list dict -> list

and the method: get_value_with_date() -> to be able to associate data to dates (with framadates)

return the values of the quantity associated to a date in a dataframe if the values are a list or a dict (only).