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dic = {}
x = "8"
for i in range(6):
    #calculate x
    dic[i] = int(str(x)+str(i))

print(dic)

{0: 80, 1: 81, 2: 82, 3: 83, 4: 84, 5: 85}

Each value of debts_list is dictionary with only 2 key-value pairs, where the keys are amount or id. I think you meant to use the id as your keys - if so, you should use the following:

new_debt_dic = {}    
for d in debts_list:
        new_debt_dic[d['id']] = d['amount']

It's not that key is a special word, but that dictionaries implement the iterator protocol. You could do this in your class, e.g. see this question for how to build class iterators.

In the case of dictionaries, it's implemented at the C level. The details are available in PEP 234. In particular, the section titled "Dictionary Iterators":

• Dictionaries implement a tp_iter slot that returns an efficient iterator that iterates over the keys of the dictionary. [...] This means that we can write

  for k in dict: ...
  

  which is equivalent to, but much faster than

  for k in dict.keys(): ...
  

  as long as the restriction on modifications to the dictionary (either by the loop or by another thread) are not violated.

• Add methods to dictionaries that return different kinds of iterators explicitly:

  for key in dict.iterkeys(): ...
  
  for value in dict.itervalues(): ...
  
  for key, value in dict.iteritems(): ...
  

  This means that for x in dict is shorthand for for x in dict.iterkeys().

In Python 3, dict.iterkeys(), dict.itervalues() and dict.iteritems() are no longer supported. Use dict.keys(), dict.values() and dict.items() instead.

I feel like consolidating info about Python dictionaries:

Creating an empty dictionary

data = {}
# OR
data = dict()

Creating a dictionary with initial values

data = {'a': 1, 'b': 2, 'c': 3}
# OR
data = dict(a=1, b=2, c=3)
# OR
data = {k: v for k, v in (('a', 1), ('b',2), ('c',3))}

Inserting/Updating a single value

data['a'] = 1  # Updates if 'a' exists, else adds 'a'
# OR
data.update({'a': 1})
# OR
data.update(dict(a=1))
# OR
data.update(a=1)

Inserting/Updating multiple values

data.update({'c':3,'d':4})  # Updates 'c' and adds 'd'

Python 3.9+:

The update operator |= now works for dictionaries:

data |= {'c':3,'d':4}

Creating a merged dictionary without modifying originals

data3 = {}
data3.update(data)  # Modifies data3, not data
data3.update(data2)  # Modifies data3, not data2

Python 3.5+:

This uses a new feature called dictionary unpacking.

data = {**data1, **data2, **data3}

Python 3.9+:

The merge operator | now works for dictionaries:

data = data1 | {'c':3,'d':4}

Deleting items in dictionary

del data[key]  # Removes specific element in a dictionary
data.pop(key)  # Removes the key & returns the value
data.clear()  # Clears entire dictionary

Check if a key is already in dictionary

key in data

Iterate through pairs in a dictionary

for key in data: # Iterates just through the keys, ignoring the values
for key, value in d.items(): # Iterates through the pairs
for key in d.keys(): # Iterates just through key, ignoring the values
for value in d.values(): # Iterates just through value, ignoring the keys

Create a dictionary from two lists

data = dict(zip(list_with_keys, list_with_values))

You can use a nice list comprehension for this:

d = dict([(row[1], row[2]) for row in iterable])

This will work in any Python version.

If you use 2.7+ or 3, you can use the cleaner dict comprehension:

d = {row[1]:row[2] for row in iterable}