How can I update values in a dictionary that is stored by a list, from strings to integers in Python?

ct_dict = {
    'fr': ['55410', '94560', '52533', '63040', '52533'],
    'de': ['73546', '64090', '60938', '75648', '60938']}

How can i change the values inside the dictionary from string to integer? For example: ['55410', '94560', '52533', '63040', '52533'] to [55410, 94560, 52533, 63040, 52533]

I tried using 2 for loops with update method but got this error:

RuntimeError: dictionary changed size during iteration

Code that got the error:

for i in ct_dict:
  for j in ct_dict[i]:
    ct_dict.update({j:int(j)})

The keys of ct_dict are i, not j, so you shouldn't use j in the .update() method.

But if you're just updating one key, just assign to that key rather than using .update().

You need to map int() over all the elements of the list.

for i, vals in ct_dict.items():
    ct_dict[i] = list(map(int, vals))

You don't actually need to update the dictionary, just change the values in the lists directly:

for nums in ct_dict.values(): 
    nums[:] = map(int,nums)

You're getting an error because you're trying to modify the dict you're using as a reference in the for loop, while the loop is executing, and you can't do that.

Solution

Assuming:

ct_dict = {
        "fr": ["55410", "94560", "52533", "63040", "52533"],
        "de": ["73546", "64090", "60938", "75648", "60938"],
    }

Best option is use to dict comprehension:

new_ct_dict = {key: [int(i) for i in values] for key, values in ct_dict.items()}

But you can also do:

new_ct_dict = {}
for key, values in ct_dict.items():
    new_ct_dict.update({key: []})
    for i in values:
        new_ct_dict[key].append(int(i))

Result:

{'fr': [55410, 94560, 52533, 63040, 52533], 'de': [73546, 64090, 60938, 75648, 60938]}

Use a for loop and a list comprehension:

my_dict = {'fr': ['55410', '94560', '52533', '63040', '52533'], 'de': ['73546', '64090', '60938', '75648', '60938']}
new_dict = {}

for key, val in my_dict.items():
    new_dict[key] = [int(item) for item in val]

print(new_dict)  # {'fr': [55410, 94560, 52533, 63040, 52533], 'de': [73546, 64090, 60938, 75648, 60938]}

Or, if you'd rather not create another dict:

my_dict = {'fr': ['55410', '94560', '52533', '63040', '52533'], 'de': ['73546', '64090', '60938', '75648', '60938']}

for key, val in my_dict.items():
    my_dict[key] = [int(item) for item in val]

print(my_dict)  # {'fr': [55410, 94560, 52533, 63040, 52533], 'de': [73546, 64090, 60938, 75648, 60938]}

For more on list comprehensions see: https://www.w3schools.com/python/python_lists_comprehension.asp

For more on the dict.items() method see: https://www.w3schools.com/python/ref_dictionary_items.asp