Learn about Dictionaries datatype for Python: A dictionary is a data type similar to arrays but works with keys and values instead of indexes. Each value stored in a dictionary can be accessed using a key, which is any type of object (a string, a number, a list, etc.) instead of using its index to address it.

For example, a database of phone numbers could be stored using a dictionary like this:

phonebook = {}
phonebook["John"] = 555477566
phonebook["Jack"] = 555377264
phonebook["Jill"] = 555662781
print(phonebook)

Trinket.io on-line Python compiler

Alternatively, a dictionary can be initialized with the same values in the following notation:

phonebook = {
    "John" : 938477566,
    "Jack" : 938377264,
    "Jill" : 947662781
}
print(phonebook)

Trinket.io on-line Python compiler

Iterating over dictionaries

Dictionaries can be iterated over, just like a list. However, a dictionary, unlike a list, does not keep the order of the values stored in it. To iterate over key-value pairs, use the following syntax:

phonebook = {"John" : 938477566,"Jack" : 938377264,"Jill" : 947662781}
for name, number in phonebook.items():
    print("Phone number of %s is %d" % (name, number))

Trinket.io on-line Python compiler

Removing a value

To remove a specified index, use either one of the following notations:

phonebook = {
   "John" : 938477566,
   "Jack" : 938377264,
   "Jill" : 947662781
}
del phonebook["John"]
print(phonebook)

Trinket.io on-line Python compiler

or:

phonebook = {
   "John" : 938477566,
   "Jack" : 938377264,
   "Jill" : 947662781
}
phonebook.pop("John")
print(phonebook)

Trinket.io on-line Python compiler

Exercise

Add “Jake” to the phonebook with the phone number 938273443, and remove Jill from the phonebook.

#this is the answer code. use online compiler below to complete the assignment on your own.
phonebook = {
    "John" : 938477566,
    "Jack" : 938377264,
    "Jill" : 947662781
}

# write your code here
phonebook["Jake"] = 938273443
del phonebook["Jill"]

# testing code
if "Jake" in phonebook:
    print("Jake is listed in the phonebook.")
if "Jill" not in phonebook:
    print("Jill is not listed in the phonebook.")

Trinket.io on-line Python compiler

 

Related Videos:

MiltonMarketing.com Related Videos.

Related Posts:

Comparing Python to other languages

Learn RE – Regular Expressions in Python

Python Serialization (JSON)

Exception Handling in Python programming

Learn Python Lists

Learn about Python Generators