遍历字典 python

Question

I am trying to write a test for a function, and create a fake dictionary to use in the test - however, I cannot work out what the format of the dictionary should be for it to work in the function. The function goes like this:

...

for data in form.cleaned_data["flows"]:
    data_point = property.MeterPoint.objects.get(id=data["id"])

I thought that the dictionary should be in the following format:

form.cleaned_data = {'flows': {"id": "1234"}}

but I keep getting this error when running the test:

    id=data["id"]
E   TypeError: string indices must be integers

Answer 1

When iterating over a dict, you get their key and not their value. Which means to access the value we have to use variable[key], you were trying, to access the key, like a dict, since the key is a string, python was assuming you tried to access a char of the string, but this can only be done with an int.

for key in form.cleaned_data["flows"]:
    data_point = property.MeterPoint.objects.get(id=form.cleaned_data["flows"][key]["id"])

Answer 2

I am not sure what framework you are using but what I can say is that if

form.cleaned_data["flow"]

is the dictionary you defined as

{"id": "1234"}

then your data variable has a type of str (string). Because looping over a dictionary is looping over the keys of dictionary. If you want to loop over values you can use .values() method eg

for data in my_dict.values():
    print(data)

If you use .values() then your data would be of type str (string) and have a value of "1234" .

Moreover you can loop over a tuple of (pair of) key-value items. for this purpose you can use .items() method. eg

for key, value in my_dict.items():
    print(key, value)

• Note about tuple unpacking: If you have a tuple such as t = (1, 2, 3) you can assign it into three variables as a, b, c = t . With this you have a = 1, b = 2, c = 3 .

Some note about the error: The error you are faceing is because type of data is probably str and for accessing index of a string you should pass an int (integer) value not a string.