Python Dictionary

In Python, a dictionary is a collection of key-value pairs, while a file is a named location on disk or in memory used to store data that can be accessed or modified.
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A dictionary is similar to a list in that it is a collection of objects.

  • Mutable
  • Dynamic (grow & shrink)
  • Nested (optionally)

Instead of elements being targed by zero based indexing like we do in a list, a dictionary uses keys.

Key:Value pairs are written within {}.

dict={key1:value1, key2:value2, key3:value3}

Looking up or setting a value in dictionary uses the [].

This would look up the value of the key foo

dict['foo']

This creates a dictionary from empty []

dict = []
dict ['a'] = 'alpha'
dict ['b'] = 'beta'
dict ['c'] = 'sigma'

print(dict)     ## {'a':'alpha', 'b':'beta', 'c':'sigma'}

Del

The del operator handles deletions.

  var = 6
  del var  # var no more!
  
  list = ['a', 'b', 'c', 'd']
  del list[0]     ## Delete first element
  del list[-2:]   ## Delete last two elements
  print(list)      ## ['b']

  dict = {'a':1, 'b':2, 'c':3}
  del dict['b']   ## Delete 'b' entry
  print(dict)      ## {'a':1, 'c':3}

References

Dictionaries in Python

Last modified July 21, 2024: update (e2ae86c)