>>> # Quiz:  write down a list of lists
... 
>>> x = [[4,5],[3],[4,5,6]]
>>> len(x)
3
>>> x[1]
[3]
>>> x[0]
[4, 5]
>>> x[2]
[4, 5, 6]
>>> x[:1]
[[4, 5]]
>>> x[1:]
[[3], [4, 5, 6]]
>>> y = [9,4]
>>> x.append(y)
>>> x
[[4, 5], [3], [4, 5, 6], [9, 4]]
>>> len(x)
4
>>> x[3]
[9, 4]
>>> x[2][0]
4
>>> 

>>> # + takes two sequences and puts them together
... 
>>> # for lists, think about this as removing the inside
... # parens
... 

>>> [1,2,3] + [4,5,6]
[1, 2, 3, 4, 5, 6]
>>> x
[[4, 5], [3], [4, 5, 6], [9, 4]]
>>> y
[9, 4]
>>> x + y
[[4, 5], [3], [4, 5, 6], [9, 4], 9, 4]
>>> 
>>> # The empty list is SOMETHING
... 
>>> y
[9, 4]
>>> y.append([])
>>> y
[9, 4, []]
>>> len(y)
3
>>> y[2]
[]
>>> # Quiz write down a list of strings

>>> # list of strings
... 
>>> x = ["jj","kk","ll"]
>>> len(x)
3
>>> len(x[0])
2
>>> y = ["a","b"]
>>> x + y
['jj', 'kk', 'll', 'a', 'b']
>>> x[0] + y[1]
'jjb'
>>> x.append(x[0] + y[1])
>>> x
['jj', 'kk', 'll', 'jjb']
>>> 
>>> # "" is something - the empty string
... 
>>> x.append("")
>>> x
['jj', 'kk', 'll', 'jjb', '']
>>> len(x)
5

>>> # Quiz - write down a list of lists of strings
... 
>>> x = [[],["jj","kk"],["a"]] 
>>> len(x)
3
>>> x[0]
[]
>>> x[1]
['jj', 'kk']
>>> x[2]
['a']

>>> len(x[1])
2
>>> x = x + [["tt","ww","xx"]]
>>> x
[[], ['jj', 'kk'], ['a'], ['tt', 'ww', 'xx']]
>>> len(x)
4
>>> x.append(["hi","there","bear"])
>>> x
[[], ['jj', 'kk'], ['a'], ['tt', 'ww', 'xx'], ['hi', 'there', 'bear']]
>>> # Quiz: write a loop that creates one big string from the
... # strings stored in x.
... 

>>> # we'll call the new string bigstr.
... 
>>> bigstr = ""
>>> for l in x:
...    for s in l:
...      bigstr += s
... 
>>> bigstr
'jjkkattwwxxhitherebear'
>>> # trace it on the board
... 

>>> #let's add print strings to understand the code
... 
>>  #and, let's work with an easier example 
x = [["aa","bb"],["cc"],[],["dd","ee"]]    
>>> bigstr = ""
>>> for l in x:
...   print("working on list",l)
...   for s in l:
...      print("bigstr so far:",bigstr,"|")
...      print("s:",s)
...      bigstr += s
...      print("bigstr after adding",s,":",bigstr)

>>> # Quiz:  define a dictionary whose keys are strings and whose
values are ints
... 
>>> x = {"jj":4,"kk":5,"zz":7}
>>> x
{'kk': 5, 'zz': 7, 'jj': 4}
>>> # does this make sense?  x[4]?
... 
>>> x[4]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 4
>>> #how do we get at the 4?
... 
>>> x["jj"]
4
>>> # Write code to print each key and its values
... 
>>> for k in x:
...   print(k,x[k])
... 
kk 5
zz 7
jj 4
>>> # write x on board, make sure they see the pieces
... 
>>> # but what if we want to print them in alphabetical
... # order by key?
... 
>>> #first, create a list of the keys
... 

>>> keys = list(x.keys())
>>> keys
['kk', 'zz', 'jj']
>>> type(keys)
<class 'list'>
>>> dir(list)
['__add__', '__class__', '__contains__', '__delattr__', '__delitem__',
>>> '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__',
>>> '__getitem__', '__gt__', '__hash__', '__iadd__', '__imul__',
>>> '__init__', '__iter__', '__le__', '__len__', '__lt__', '__mul__',
>>> '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__',
>>> '__reversed__', '__rmul__', '__setattr__', '__setitem__',
>>> '__sizeof__', '__str__', '__subclasshook__', 'append', 'count',
>>> 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']
>>> #see the sort?
... 
>>> help(list.sort)
Help on method_descriptor:

sort(...)
    L.sort(key=None, reverse=False) -- stable sort *IN PLACE*

>>> keys.sort()
>>> keys
['jj', 'kk', 'zz']
>>> # now, let's print
... 
>>> for k in keys:
...   print(k,x[k])
... 
jj 4
kk 5
zz 7
>>> 

>>> # reminder about the functions that convert between types.  Python
... #  will do the conversion if it can make sense of it.
... 
>>> float("3")
3.0
>>> float(3)
3.0
>>> int("34")
34
>>> str(34)
'34'
>>> str(54.3)
'54.3'
>>> list("hello there bear")
['h', 'e', 'l', 'l', 'o', ' ', 't', 'h', 'e', 'r', 'e', ' ', 'b', 'e',
'a', 'r']
>>> list("54.3")
['5', '4', '.', '3']
>>> 
>>> list("hello there bear")
['h', 'e', 'l', 'l', 'o', ' ', 't', 'h', 'e', 'r', 'e', ' ', 'b', 'e',
'a', 'r']
>>> list("54.3")
['5', '4', '.', '3']
>>> 
>>> 
>>> 
>>> #remember our dictionary x?
... 
>>> x
{'kk': 5, 'zz': 7, 'jj': 4}
>>> x.keys()
dict_keys(['kk', 'zz', 'jj'])
>>> list(x.keys())
['kk', 'zz', 'jj']
>>> 

>>> # write code to sum the numbers stored in x
... 
>>> x
{'kk': 5, 'zz': 7, 'jj': 4}

>>> sum = 0
>>> for k in x:
...   sum += x[k]
... 
>>> sum
16
>>> 

>>> # quiz:  define a dictionary whose keys are strings
... #   and whose values are lists of ints
... 
>>> x = {"kk":[1,2,3],"jj":[0],'ll':[]}
>>> x
{'kk': [1, 2, 3], 'll': [], 'jj': [0]}
>>> x['kk']
[1, 2, 3]
>>> len(x['jj'])
1
>>> len(x['ll'])
0
>>> x['jj'] + x['kk']
[0, 1, 2, 3]
>>> x['ll']
[]
>>> x['ll'].append(54)
>>> x
{'kk': [1, 2, 3], 'll': [54], 'jj': [0]}
>>> x['ll'].append(33)
>>> x
{'kk': [1, 2, 3], 'll': [54, 33], 'jj': [0]}
>>> len(x['ll'])
2
>>> # write code to sum all the ints stored in x

>>> sum = 0
>>> for k in x:
...   for i in x[k]:
...      sum += i
... 
>>> sum
93
>>> #trace that for the first few.

# To set up for the next thing...
>>> # remember Python let's you do things like this
... 
>>> one,two = [1,2]
>>> one
1
>>> two
2
>>> one,two = [1,2,3]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: too many values to unpack (expected 2)
>>> 

#Python makes sense of it if it can

====
phone = {'555-7632': 'Paul', '555-9832': 'Andrew',\
             '555-6677': 'Jen', '555-9823': 'Michael',\
             '555-6342' : 'Wael', '555-7343' : 'Paul',\
             '555-2222' : 'Michael'}
    
>>> from phoneDictEG import phone  # for those who are interested,
    # you can do this, and then you don't have to say
    # phoneDictEG.phone
    # You don't have to know this, though

>>> phone
{'555-7632': 'Paul', '555-9832': 'Andrew', '555-7343': 'Paul',
'555-9823': 'Michael', '555-6342': 'Wael', '555-6677': 'Jen',
'555-2222': 'Michael'}
>>> # So, we have a dictionary where the keys and values are both
strings
... 
>>> phone.keys()
dict_keys(['555-7632', '555-9832', '555-7343', '555-9823', '555-6342',
'555-6677', '555-2222'])
>>> phone.items()
dict_items([('555-7632', 'Paul'), ('555-9832', 'Andrew'), ('555-7343',
'Paul'), ('555-9823', 'Michael'), ('555-6342', 'Wael'), ('555-6677',
'Jen'), ('555-2222', 'Michael')])
>>> phone['555-7632']
'Paul'
>>> len(phone['555-7632']) # be careful - maybe tricky!
4
>>> 
>>> phone
{'555-7632': 'Paul', '555-9832': 'Andrew', '555-7343': 'Paul',
'555-9823': 'Michael', '555-6342': 'Wael', '555-6677': 'Jen',
'555-2222': 'Michael'}
>>> len(phone)
7

>>> # Paul's phone numbers
... 
>>> # note there are 2 
... 
>>> # Quiz:  write code to find Paul's phone numbers
... 
>>> for k in phone:
...    if phone[k] == "Paul":
    # oops, what do we do now?  We are supposed
    # to be gathering up Paul's phone numbers.
    # if the if is true, then .. what are we adding
    # this number to?
# start over

>>> nums = []
>>> for k in phone:
...    if phone[k] == "Paul":
...       nums.append(phone[k])
... 
>>> nums
['Paul', 'Paul']
>>> # oops - what did we do wrong?
... 
>>> 
>> # try again!
... 
>>> nums = []
>>> for k in phone:
...    if phone[k] == "Paul":
...      nums.append(k)
... 
>>> nums
['555-7632', '555-7343']
>>> 
#ok, good

>>> # remember, here is our dict
... 
>>> phone
{'555-7632': 'Paul', '555-9832': 'Andrew', '555-7343': 'Paul',
'555-9823': 'Michael', '555-6342': 'Wael', '555-6677': 'Jen',
'555-2222': 'Michael'}
>>> #let's create a new dictionary that is indexed by person
... 
>>> # it's common to have multiple dictionaries containing the same
data in different
... # forms.  you might need to access the information differently for
different purposes
... 
>>> #what does that mean?
... 
>>> #QUIZ:  what will the keys be?  Write down one of the keys
... 
>>> 'Paul' #etc
'Paul'
>>> #QUIZ: the values will be what type?
... 
>>> # string, e.g., '555-9832'
... 
>>> # no - some people have more than one phone number!
... 

>>> #remember, here are Paul's phone numbers  
... 
>>> nums
['555-7632', '555-7343']
>>> #so, the values are lists of ...
... 
>>> # the values are lists of strings       
... 
>>> #for example, phone['Paul'] should be
... 
>>> nums
['555-7632', '555-7343']
>>> 
>>> phone
{'555-7632': 'Paul', '555-9832': 'Andrew', '555-7343': 'Paul',
'555-9823': 'Michael', '555-6342': 'Wael', '555-6677': 'Jen',
'555-2222': 'Michael'}
>>> #what should phone['Andrew'] be?
... 
>>> ['555-7343']
['555-7343']

>>> phoneByName = {} # this is how you create an empty dict
>>> # some reminders
... 
>>> phone.items()
dict_items([('555-7632', 'Paul'), ('555-9832', 'Andrew'), ('555-7343',
>>> 'Paul'), ('555-9823', 'Michael'), ('555-6342', 'Wael'),
>>> ('555-6677', 'Jen'), ('555-2222', 'Michael')])
>>> number,name = ('555-6677','Jen')
>>> number
'555-6677'
>>> name
'Jen'
>>> if 'Jen' in phoneByName:
...    print('yes')
... else:
...    print('no')
... 
no
>>> phoneByName
{}
>>> #ok!
... 
>>> if 'Jen' in phone:
...    print('yes')
... else:
...    print('no')
... 
no
>>> phone
{'555-7632': 'Paul', '555-9832': 'Andrew', '555-7343': 'Paul',
>>> '555-9823': 'Michael', '555-6342': 'Wael', '555-6677': 'Jen',
>>> '555-2222': 'Michael'}
>>> if '555-7632' in phone:
...    print('yes')
... else:
...    print('no')
... 
yes
>>> #ok, just messing with you, to remind you what 'in' means
... 
>>> # so, we are building a dictionary indexed by name, with values
... #  the list of phone numbers for that person
... 
>>> phone
{'555-7632': 'Paul', '555-9832': 'Andrew', '555-7343': 'Paul',
>>> '555-9823': 'Michael', '555-6342': 'Wael', '555-6677': 'Jen',
>>> '555-2222': 'Michael'}

>>> phone.items()
dict_items([('555-7632', 'Paul'), ('555-9832', 'Andrew'), ('555-7343',
>>> 'Paul'), ('555-9823', 'Michael'), ('555-6342', 'Wael'),
>>> ('555-6677', 'Jen'), ('555-2222', 'Michael')])
>>> for number,name in phone.items():
...    if name in phoneByName:
...       phoneByName[name].append(number)
...    else:
...       phoneByName[name] = [number]
... 

>>> phoneByName
{'Jen': ['555-6677'], 'Paul': ['555-7632', '555-7343'], 'Wael':
['555-6342'], 'Michael': ['555-9823', '555-2222'], 'Andrew':
['555-9832']}

[recall:  inverted_dict.py already on the schedule]