Python for Data Science: Dictionary

Like lists, Dictionaries are collections of many values. But in the lists, we have indexes whereas in dictionaries we can use any kind of data type, be it a string or integer or float.

The indexes, whatever we use in the dictionary are called keys and the keys with the associated values are called key-value pairs. It's one of the most used data-structure in the world.

dict = {}

dict = {key : value}

Here I showed some basic concepts and methods.

# empty dictionary
 
 dict1 = dict()
 dict1
 {}
 
 dict2 = {}
 dict2
 {}
 
 #create dictionary
 
 diction = {1:"one", 2:"two", 3:"three"}
 diction
 {1: 'one', 2: 'two', 3: 'three'}
 
 diction = dict({1:"one", 2:"two", 3:"three"})
 diction
 {1: 'one', 2: 'two', 3: 'three'}
 
 # Return Dictionary Keys using keys() method
 mydict = {1:"one", 2:"two", 3:"three"}
 mydict.keys()
 dict_keys([1, 2, 3])
 
 # Return Dictionary Values using values() method
 mydict.values()
 dict_values(['one', 'two', 'three'])

# Access item using key
 mydict = {1:"one", 2:"two", 3:"three", 4:"four"}
 mydict[2]
 'two'
 
 # Access item using key using get() method
 mydict.get(3)
 'three'
 

String type value must be covered by single/double quotation.

mydict = {'Name': "Rifat", "Id": 134670, "DOB": 1990, "Address":'Bangladesh'}
 mydict
 {'Name': 'Rifat', 'Id': 134670, 'DOB': 1990, 'Address': 'Bangladesh'}
 
 # Adding Items
 
 mydict["Job"] = "Data Scientist"
 mydict
 {'Name': 'Rifat',
  'Id': 134670,
  'DOB': 1990,
  'Address': 'Bangladesh',
  'Job': 'Data Scientist'}
 
  # Update Items
 
  mydict["DOB"] = 1991
  mydict
  {'Name': 'Rifat',
  'Id': 134670,
  'DOB': 1991,
  'Address': 'Bangladesh',
  'Job': 'Data Scientist'}
 
  # Removing items in the dictionary using Pop method
 
  mydict.pop('Job')
  mydict
  {'Name': 'Rifat', 'Id': 134670, 'DOB': 1991, 'Address': 'Bangladesh'}
 
  # Removing item using del method
  del[mydict["Id"]]
  mydict
  {'Name': 'Rifat', 'DOB': 1991, 'Address': 'Bangladesh'}
 
  # Delete all items of the dictionary using clear method
 
  mydict.clear()
  mydict
  {'Name': 'Rifat', 'DOB': 1991, 'Address': 'Bangladesh'}
 

mydict = {'Name': "Rifat", "Id": 134670, "DOB": 1990, "Address":'Bangladesh'}
 for i in mydict:
  print(mydict[i])
 Rifat
 134670
 1990
 Bangladesh

square = {i:i*2 for i in range(10)}
 square
 {0: 0, 1: 2, 2: 4, 3: 6, 4: 8, 5: 10, 6: 12, 7: 14, 8: 16, 9: 18}
 
 mydict = {'Name': "Rifat", "Id": 134670, "DOB": 1990, "Address":'Bangladesh'}
 mydict1 = {k:v for (k,v) in mydict.items()}
 mydict
 {'Name': 'Rifat', 'Id': 134670, 'DOB': 1990, 'Address': 'Bangladesh'}