Python

#Creating dictionaries dict1 = {'color': 'blue', 'shape': 'square', 'volume':40} dict2 = {'color': 'red', 'edges': 4, 'perimeter':15} #Creating new pairs and updating old ones dict1['area'] = 25 #{'color': 'blue', 'shape': 'square', 'volume': 40, 'area': 25} dict2['perimeter'] = 20 #{'color': 'red', 'edges': 4, 'perimeter': 20} #Accessing values through keys print(dict1['shape']) #You can also use get, which doesn't cause an exception when the key is not found dict1.get('false_key') #returns None dict1.get('false_key', "key not found") #returns the custom message that you wrote #Deleting pairs dict1.pop('volume') #Merging two dictionaries dict1.update(dict2) #if a key exists in both, it takes the value of the second dict dict1 #{'color': 'red', 'shape': 'square', 'area': 25, 'edges': 4, 'perimeter': 20} #Getting only the values, keys or both (can be used in loops) dict1.values() #dict_values(['red', 'square', 25, 4, 20]) dict1.keys() #dict_keys(['color', 'shape', 'area', 'edges', 'perimeter']) dict1.items() #dict_items([('color', 'red'), ('shape', 'square'), ('area', 25), ('edges', 4), ('perimeter', 20)])

student_data = { "name":"inderpaal", "age":21, "course":['Bsc', 'Computer Science'] } #the keys are the left hand side and the values are the right hand side #to print data you do print(name_of_dictionary['key_name']) print(student_data['name']) # will print 'inderpaal' print(student_data['age']) # will print 21 print(student_data['course'])[0] #this will print 'Bsc' since that field is an array and array[0] is 'Bsc'

#title :Dictionary Example #author :Josh Cogburn #date :20191127 #github :https://github.com/josh-cogburn #==================================================== thisdict = { "brand": "Ford", "model": "Mustang", "year": 1964 } #Assigning a value thisdict["year"] = 2018

# dictionary refresh new_dict = { "first":"1,2,3", "second":"321", "third":"000", } # adding to dictionary new_dict.update({"fourth":"D"}) print(new_dict) #removing from dictionary new_dict.pop("first") print(new_dict) new = {"five":"888"} #updating a dictionary new_dict.update(new) print(new_dict)

<view> = <dict>.keys() # Coll. of keys that reflects changes. <view> = <dict>.values() # Coll. of values that reflects changes. <view> = <dict>.items() # Coll. of key-value tuples that reflects chgs. value = <dict>.get(key, default=None) # Returns default if key is missing. value = <dict>.setdefault(key, default=None) # Returns and writes default if key is missing. <dict> = collections.defaultdict(<type>) # Creates a dict with default value of type. <dict> = collections.defaultdict(lambda: 1) # Creates a dict with default value 1. <dict> = dict(<collection>) # Creates a dict from coll. of key-value pairs. <dict> = dict(zip(keys, values)) # Creates a dict from two collections. <dict> = dict.fromkeys(keys [, value]) # Creates a dict from collection of keys. <dict>.update(<dict>) # Adds items. Replaces ones with matching keys. value = <dict>.pop(key) # Removes item or raises KeyError. {k for k, v in <dict>.items() if v == value} # Returns set of keys that point to the value. {k: v for k, v in <dict>.items() if k in keys} # Returns a dictionary, filtered by keys.

# Creating an empty Dictionary Dict = {} print("Empty Dictionary: ") print(Dict) # Creating a Dictionary # with dict() method Dict = dict({1: 'Geeks', 2: 'For', 3:'Geeks'}) print(" Dictionary with the use of dict(): ") print(Dict) # Creating a Dictionary # with each item as a Pair Dict = dict([(1, 'Geeks'), (2, 'For')]) print(" Dictionary with each item as a pair: ") print(Dict)

txt = "this is a wild string"

print(txt.replace("i", "x"))  # print string with all i characters replaced with x
print(txt.replace("i", "x", 2))  # print string with first two i characters found with x
print(txt.upper())  # print string in all uppercase letters
print(txt.lower())  # print string in all uppercase letters

print(ord('A'))  # print the ordinal value of a character
print(chr(95))  # print character from its ordinal value
print('Yes' * 5) # print string Yes 5 times

# Reference strings by index
print(txt[0])  # print first letter of string from starting index
print(txt[0:2])  # print first two letters from starting index
print(txt[1:])  # print all characters except the first letter
print(txt[0::2])  # print every second character
print(txt[::-1])  # print string in reverse
print(txt[-1])  # print the last character in a string
print(txt[-2:])  # print the last who characters in a string

# check if a wild is found in txt
if "wild" in txt:
  print("wild is found in txt")

# check if a blah is not found in txt
if "blah" not in txt:
  print("is not found in txt")

# Check if txt starts with this
if txt.startswith("this"):
  print("Starts with this")

# check if txt ends with ing
if txt.endswith("ing"):
  print("Ends with ing")

# Split a string into a tuple when the delimiter is first encountered
txt = 'random-data'

data_split = txt.partition('-')
print(data_split)
# output ('random', '-', 'data')

len(txt)  # Return length of string

# loop through each character in string
for char in txt:
  print(char)

# Display price with commas and 2 digit precision
price = 9749000
display_price = f"My price {price:,.2f}"
print(display_price)


fruits = ['orange', 'apple', 'pear', 'banana', 'kiwi', 'apple', 'banana']
fruits.count('apple')  # count number of apples found in list
# output 2
fruits.count('tangerine')  # count number of tangerines in list
# output 0
fruits.index('banana')  # find the first index of banana
# output 3
fruits.index('banana', 4)  # Find next banana starting a position 4
# output 6
fruits.reverse()  # reverse fruits array
fruits
# output ['banana', 'apple', 'kiwi', 'banana', 'pear', 'apple', 'orange']
fruits.append('grape')  # append grape at the end of array
fruits
# output ['banana', 'apple', 'kiwi', 'banana', 'pear', 'apple', 'orange', 'grape']
fruits.sort()
fruits
# output ['apple', 'apple', 'banana', 'banana', 'grape', 'kiwi', 'orange', 'pear']

len(fruits)  # length of fruits array
# output 8

# loop and print each fruit
for fruit in fruits:
  print(fruit)
  
empty_set = set()

basket = {'apple', 'orange', 'apple', 'pear', 'orange', 'banana'}
print(basket)                      # show that duplicates have been removed
# output {'orange', 'banana', 'pear', 'apple'}

# check if orange is in basket set
print('orange' in basket)
# output true

# convert a string to a set of letters - sets contains no duplicates
set_a = set('abcd')
set_b = set('bcde')

# the operations below returns new sets
# print letters in set_a but not in set_b - difference
print(set_a - set_b)
# output {'a'}

# print set letters that is in either set a or b - union
print(set_a | set_b)
# output {'a', 'c', 'e', 'b', 'd'}

# print letters that are in both set_a and set_b - intersection
print(set_a & set_b)
# output {'c', 'd', 'b'}

# print letters that are in set_a and set_b when the letters are found in a set but no the other set - symmetric_difference()
print(set_a ^ set_b)
# output {'a', 'e'}

# Creating dictionaries
dict1 = {'color': 'blue', 'shape': 'square', 'volume': 40}
dict2 = {'color': 'red', 'edges': 4, 'perimeter': 15}

# Creating new pairs and updating old ones
dict1['area'] = 25  # {'color': 'blue', 'shape': 'square', 'volume': 40, 'area': 25}
dict2['perimeter'] = 20  # {'color': 'red', 'edges': 4, 'perimeter': 20}

# Accessing values through keys - an KeyError will occur if the key does not exists
print(dict1['shape'])

# You can also use get, which doesn't cause an exception when the key is not found
dict1.get('false_key')  # returns None
dict1.get('false_key', "key not found")  # returns the custom message that you wrote

# Delete item key and return the value if the key does not exists a KeyError occurs
print(dict1.pop('volume'))

# Merging two dictionaries
dict1.update(dict2)  # if a key exists in both, it takes the value of the second dict
dict1  # {'color': 'red', 'shape': 'square', 'area': 25, 'edges': 4, 'perimeter': 20}

# Getting only the values, keys or both (can be used in loops)
dict1.values()  # dict_values(['red', 'square', 25, 4, 20])
dict1.keys()  # dict_keys(['color', 'shape', 'area', 'edges', 'perimeter'])
dict1.items()
# dict_items([('color', 'red'), ('shape', 'square'), ('area', 25), ('edges', 4), ('perimeter', 20)])

# create a shallow copy of dict1
dict3 = dict1.copy()
# dict3 = {'color': 'red', 'shape': 'square', 'area': 25, 'edges': 4, 'perimeter': 20}

# A dict (dictionary) is a data type that store keys/values myDict = {"name" : "bob", "language" : "python"} print(myDict["name"]) # Dictionaries can also be multi-line otherDict { "name" : "bob", "phone" : "999-999-999-9999" }

#Python dictionaries consists of key value pairs tha #The following is an example of dictionary state_capitals = { 'Arkansas': 'Little Rock', 'Colorado': 'Denver', 'California': 'Sacramento', 'Georgia': 'Atlanta' } #Adding items to dictionary #Modification of the dictionary can be done in similar maner state_capitals['Kampala'] = 'Uganda' #Kampala is the key and Uganda is the value #Interating over a python dictionary for k in state_capitals.keys(): print('{} is the capital of {}'.format(state_capitals[k], k))

stationary_items = { "Pencil":"Pencil is used to write things in copy", "Eraser": "Eraser is used to remove the written things", "Sharpner":"This is used to sharp your pencil" } print(stationary_items["Pencil"])