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#+TITLE: Dictionaries
#+AUTHOR: FOSSEE
#+EMAIL: info@fossee.in   
#+DATE:    

#+DESCRIPTION: 
#+KEYWORDS: 
#+LANGUAGE:  en
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* Outline
  - Creating dictionaries
    - empty dictionaries
    - with data
  - Keys and values
  - Checking for elements
  - Iterating over elements

* Overview of Dictionaries
  - A dictionary contains meaning of words
    - /Word/ is the /key/ here.
    - /Meaning/ is the /value/ here.
  - A Key-Value pair data structure
    - Provide key-value mappings

* Creating dictionary
  - Empty dictionary
    - ~mt_dict = {}~
      - ~[]~ - lists
      - ~{}~ - dictionaries
  - With data
    #+begin_src python
        extensions = {'jpg' : 'JPEG Image', 
	              'py' : 'Python script',
                      'html' : 'Html document', 
                      'pdf' : 'Portable Document Format'}
    #+end_src

   *Note* - ordering in dictionaries cannot be relied on
* Accessing Elements
  - syntax
    : extensions[key]
  
  : In []: print extensions['jpg']
  : Out []: JPEG Image
  : In []: print extensions['zip']
* Adding and Deleting values
  - Adding a new value
    : In []: extension['cpp'] = 'C++ code'
    adds a new key /cpp/ with /C++ code/ as value
  - Deleting values
    : In []: del extensions['pdf']
    deletes the key-value pair identified by /pdf/
  - Changing value associated with a key
    : In []: extension['cpp'] = 'C++ source code'
    changes the value of the existing key
* Checking for container-ship of keys
  : In []: 'py' in extensions
  : Out []: True
  Returns *True* if the /key/ is found.
  : In []: 'odt' in extensions
  : Out []: False
  Returns *False* if the /key/ is not found.

* Retrieve keys and values
  - ~.keys()~ method
    : In []: extensions.keys()
    Returns a list of keys in the dictionary.
  - ~.values()~ method
    : In []: extensions.values()
    Returns the list of values in the dictionary.
* Exercise 1
  Print the keys and values in the dictionary one by one.
* Summary
  - Creating dictionaries
    - empty dictionaries
    - with data
  - ~.keys()~ method
  - ~.values()~ method
  - Iterating over dictionaries
* Thank you!
#+begin_latex
  \begin{block}{}
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  This spoken tutorial has been produced by the
  \textcolor{blue}{FOSSEE} team, which is funded by the 
  \end{center}
  \begin{center}
    \textcolor{blue}{National Mission on Education through \\
      Information \& Communication Technology \\ 
      MHRD, Govt. of India}.
  \end{center}  
  \end{block}
#+end_latex