Python - Dictionary

dictionary.py

# A dictionary is a collection which is unordered, changeable and indexed. 
# In Python dictionaries are written with curly brackets, and they have keys and values.
thisdict =	{
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}
print(thisdict)

# You can access the items of a dictionary by referring to its key name, inside square brackets:
x = thisdict["model"]
x = thisdict.get("model")

# You can change the value of a specific item by referring to its key name:
thisdict =	{
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}
thisdict["year"] = 2018

# You can loop through a dictionary by using a for loop.
# When looping through a dictionary, the return value are the keys of the dictionary, 
# but there are methods to return the values as well.
for x in thisdict:
  print(x) # prints all the keys one by one
  print(thisdict[x]) # prints all values one by one
  
for x in thisdict.values():
  print(x) # prints all values one by one

# Loop through both keys and values, by using the items() function:
for x, y in thisdict.items():
  print(x, y)
  
# To determine if a specified key is present in a dictionary use the in keyword:
thisdict =	{
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}
if "model" in thisdict:
  print("Yes, 'model' is one of the keys in the thisdict dictionary")
  
# To determine how many items (key-value pairs) a dictionary has, use the len() method.
print(len(thisdict))

# Adding an item to the dictionary is done by using a new index key and assigning a value to it:
thisdict =	{
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}
thisdict["color"] = "red"
print(thisdict)

# There are several methods to remove items from a dictionary:
# The pop() method removes the item with the specified key name:
thisdict =	{
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}
thisdict.pop("model")
print(thisdict)

# The popitem() method removes the last inserted item (in versions before 3.7, a random item is removed instead):
thisdict =	{
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}
thisdict.popitem()
print(thisdict)

# The del keyword removes the item with the specified key name:
thisdict =	{
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}
del thisdict["model"]
print(thisdict)

# The del keyword can also delete the dictionary completely:
del thisdict

# The clear() keyword empties the dictionary:
thisdict =	{
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}
thisdict.clear()
print(thisdict)