Styjun

I ask the user of my program to input the number of datasets he/she wants to investigate, e.g. three datasets. Accordingly, I should then create three dictionaries (dataset_1, dataset_2, and dataset_3) to hold the values for the various parameters. Since I do not know beforehand the number of datasets the user wants to investigate, I have to create and name the dictionaries within the program.

Apparently, Python does not let me do that. I could not rename the dictionary once it has been created.

I have tried using os.rename("oldname", "newname"), but that only works if I have a file stored on my computer hard disk. I could not get it to work with an object that lives only within my program.

number_sets = input('Input the number of datasets to investigate:')

for dataset in range(number_sets):
 init_dict = 
 # create dictionary name for the particular dataset
 dict_name = ''.join(['dataset_', str(dataset+1)])
 # change the dictionary´s name
 # HOW CAN I CHANGE THE DICTIONARY´S NAME FROM "INIT_DICT"
 # TO "DATASET_1", WHICH IS THE STRING RESULT FOR DICT_NAME?

I would like to have in the end

dataset_1 =
dataset_2 =

and so on.

You don't (need to). Keep a list of data sets.

datasets = []
for i in range(number_sets):
 init_dict = 
 ...
 datasets.append(init_dict)

Then you have datasets[0], datasets[1], etc., rather than dataset_1, dataset_2, etc.

Inside the loop, init_dict is set to a brand new empty directory at the top of each iteration, without affecting the dicts added to datasets on previous iterations.

If you want to create variables like that you could use the globals

number_sets = 2
for dataset in range(number_sets):
 dict_name = ''.join(['dataset_', str(dataset+1)])
 globals() [dict_name] = 

print(dataset_1)
print(dataset_2)

However this is not a good practice, and it should be avoided, if you need to keep several variables that are similar the best thing to do is to create a list.

You can use a single dict and then add all the data sets into it as a dictionary:

all_datasets = 

for i in range(number_sets):
 all_datasets['dataset'+str(i+1)] = 

And then you can access the data by using:

all_datasets['dataset_1']

This question gets asked many times in many different variants (this is one of the more prominent ones, for example). The answer is always the same:

It is not easily possible and most of the time not a good idea to create python variable names from strings.

The more easy, approachable, safe and usable way is to just use another dictionary. One of the cool things about dictionaries: any object can become a key / value. So the possibilities are nearly endless. In your code, this can be done easily with a dict comprehension:

number_sets = int(input('Input the number of datasets to investigate:')) # also notice that you have to add int() here
data = ''.join(['dataset_', str(dataset + 1)]): for dataset in range(number_sets)
print(data)

>>> 5
'dataset_1': , 'dataset_2': , 'dataset_3': , 'dataset_4': , 'dataset_5': 

Afterwards, these dictionaries can be easily accessed via data[name_of_dataset]. Thats how it should be done.