#!/usr/bin/env python
# coding: utf-8

# # Dictionaries
# - another compound type/container like lists and tuples
# - very useful data structure/container that can store data as lookup table 
# - Python's mapping type similar to `map` container, or associative arrays in C++ and other languages
# - dict maps keys (immutable type) to values of any type (heterogenous)
# - Python uses complex hash algorithm to index key for fast access (Worst case "Big-Oh": $O(1)$), as a result the ordering is not maintained

# ## creating dictionary objects

# In[3]:


eng2sp = {} # or
eng2sp1 = dict()


# In[2]:


print(eng2sp, eng2sp1)


# In[21]:


eng2sp["One"] = "uno"
eng2sp["two"] = "dos"
eng2sp["three"] = "tres"
eng2sp[4] = "quatro"
eng2sp["five"] = "sinco"


# In[ ]:


key = 'Five'
eng2sp[key] = 'Sinco'


# In[4]:


print(eng2sp)


# In[7]:


print(eng2sp['One'])


# In[8]:


symbolNames = {'*':'asterick', '+':"plus", '-': 'minus'}


# In[9]:


print(eng2sp, symbolNames)


# In[10]:


dict1 ={'one': 'uno', 'two': 'dos', 'three': 'tres', '4': 'quatro', 'five': 'sinco'}


# ## accessing values
# - use index operator ['key'] 
# - dict is mutable

# In[12]:


one = 'One'


# In[13]:


eng2sp[one]


# In[18]:


eng2sp['ten'] = 'diez'
print(eng2sp['ten'])


# In[25]:


eng2sp['One'] = 'Uno'


# In[30]:


eng2sp['One'] = ['uno']


# In[33]:


eng2sp['One'].append('Uno')


# In[34]:


print(eng2sp)


# In[35]:


adict = {1: ['uno', 'one'], 2:('two', 'dos'), 3:{'three':'tres'}}


# In[37]:


# How do you access tres in adict?
print(adict[1][1])
print(adict[3]['three'])


# ## dictionary methods

# In[1]:


help(dict)


# In[5]:


for k in eng2sp.keys(): # the order of the keys is not defined
    print("key {} maps to value {}".format(k, eng2sp[k]))


# In[6]:


# iterate over keys
for k in eng2sp:
    print('key = {} value = {}'.format(k, eng2sp[k]))


# In[7]:


# iterate over values
for val in eng2sp.values():
    print("value = ", val)


# In[8]:


values = list(eng2sp.values())


# In[9]:


values


# In[10]:


items = list(eng2sp.items())


# In[11]:


print(items)


# In[12]:


dict2 = dict(items)
print(dict2)


# In[13]:


for k, v in eng2sp.items():
    print('{} -> {}'.format(k, v))


# In[19]:


print(eng2sp.popitem())
print(eng2sp)


# ## checking if key exists
# - in and not in operators can be used to check for keys

# In[23]:


"One" in eng2sp


# In[25]:


"Ten" in eng2sp


# In[26]:


"twenty" not in eng2sp


# # copying dictionary objects
# - shallow copy vs deep copy

# In[ ]:


import copy
digits = {1: 'one', 2: 'two', 3: ['three', 'Three', 'THREE']}
digits1 = digits # creates an alias
digits2 = digits.copy() # shallow copy
digits3 = copy.deepcopy(digits) # deep copy


# ### visualize in pythontutor.com: 
# - https://goo.gl/XmvYkB

# In[8]:


from IPython.display import IFrame
src = '''
http://pythontutor.com/iframe-embed.html#code=import%20copy%0Adigits%20%3D%20%7B1%3A%20'one',%202%3A%20'two',%203%3A%20%5B'three',%20'Three',%20'THREE'%5D%7D%0Adigits1%20%3D%20digits%20%23%20creates%20an%20alias%0Adigits2%20%3D%20digits.copy%28%29%20%23%20shallow%20copy%0Adigits3%20%3D%20copy.deepcopy%28digits%29%20%23%20deep%20copy&codeDivHeight=400&codeDivWidth=350&cumulative=false&curInstr=0&heapPrimitives=false&origin=opt-frontend.js&py=3&rawInputLstJSON=%5B%5D&textReferences=false
'''
IFrame(src, width=900, height=600)


# ## passing dict to function
# - dict is a mutable type
# - dict objects are passed by reference

# In[3]:


# find the histogram (frequency of each unique character) in a word
def histogram(word, hist):
    for c in word:
        c = c.lower()
        if c in hist:
            hist[c] += 1
        else:
            hist[c] = 1


# In[4]:


h = {}
histogram('Mississippim', h)
for k, v in h.items():
    print(k, v)


# ## returning dict from functions
# - dict objects can be returned from functions

# In[6]:


def getHist(word):# = "Mississippi"
    h = {}
    for c in word:
        if c in h:
            h[c] += 1
        else:
            h[c] = 1
    return h


# In[7]:


hist = getHist('Mississippi')
print(hist)
if 'M' in hist:
    print('M is in histogram')


# ## Exercises

# ### exercise 1
# Count and print letter frequency in some words. Hint: use get method
# 

# ### exercise 2
# Write a program that reads a string and returns a table of the letters of the alphabet in alphabetical order which occur in the string together with the number of times each letter occurs. Case should be ignored. A sample output of the program when the user enters the data “ThiS is String with Upper and lower case Letters”, would look this:
# <pre>
# a  2
# c  1
# d  1
# e  5
# g  1
# h  2
# i  4
# l  2
# n  2
# o  1
# p  2
# r  4
# s  5
# t  5
# u  1
# w  2
# </pre>

# In[ ]: