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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

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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}

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