You can use mydict in a for loop to check each key, and modify the value if necessary. Something like for key in mydict:

No. Keys and values are not guaranteed to be ordered in the general case. In Python 3.6 and up, keys and values will retain order, but you shouldn't rely on that unless you want your code to only ever run on 3.6 and up. If you want something that works consistently across all Python versions, use collections.OrderedDict.

Dictionaries in Python are usually just used as a data structure. If you want to work with some interesting data, search for "datasets" online and you'll find some stuff that you can put into a dictionary yourself.

Dictionaries are super handy for when you want a list of items accessible by a related piece of data. For example, if you were going to write something to calculate the number of each letter in a sentence, you might do something like this.

# text = my comment
characters = {}

for character in text.lower():
	if character in characters:
     	characters[character] += 1
	else:
		characters[character] = 1

for k, v in characters.items():
	print k, v

And the output:

   43
 , 2
 . 2
 a 15
 c 8
 b 3
 e 28
 d 5
 g 5
 f 6
 i 16
 h 8
 k 1
 m 6
 l 8
 o 15
 n 11
 p 3
 s 10
 r 10
 u 6
 t 18
 w 4
 y 5
 x 1

For the record, you can also do the sum with a dictionary expression.

characters = {char: text.count(char) for char in text}

Does that answer your question a bit? In this case, we used a dict so we could easily refer to the number of any given character in text by the character. We could also use a list of tuples, but we would have to iterate the list to find the position of the relevant entry.