**Prerequisite – **Python Basics** **

Ever wondered how the most popular social networking site Facebook works? How we are connected with friends using just Facebook? So, Facebook and other social networking sites work on a methodology called social networks. Social networking is used in mostly all social media sites such as Facebook, Instagram, and LinkedIn, etc. It has a significant effect on marketers to engage customers. Social networks use graphs for creating a network. Their nodes are people and edges are their connection between each other. Two nodes with edges connected are friends. Now let’s see an example for understanding what is social networks.

The network of 50 students in a class

The most important python library used in social networking is **Networkx.**

**NetworkX**

NetworkX is a graph package that is used to create and modify different types of graphs. It provides a rapid development environment for collaborative, multidisciplinary projects.

#### Installation:

pip install networkx

After starting python, we have to import networkx module:

import networkx as nx

#### Basic inbuilt graph types are:

**Graph:**This type of graph stores nodes and edges and edges are un-directed. It can have self-loops but cannot have parallel edges.**Di-Graph:**This type of graph is the base class for directed graphs. It can have nodes and edges and edges are directed in nature. It can have self-loops but parallel edges are not allowed in Di-Graph.**Multi-Graph:**This type of graph is an undirected graph class that can store multi or parallel edges. It can have self-loops as well. Multi-edges are multiple edges between 2 nodes.**Multi-DiGraph:**This type of graph is a directed graph class that can store multi edges. It can have self-loops as well. Multi-edges are multiple edges between 2 nodes.

#### Example of Graph creation :

## Python3

`# import networkx library` `import` `networkx as nx` ` ` `# create an empty undirected graph ` `G ` `=` `nx.Graph()` ` ` `# adding edge in graph G` `G.add_edge(` `1` `, ` `2` `)` `G.add_edge(` `2` `, ` `3` `, weight` `=` `0.9` `)` |

#### Drawing of graph:

Drawing can be done using Matplotlib.pyplot library.

## Python3

`# import matplotlib.pyplot library` `import` `matplotlib.pyplot as plt` ` ` `# import networkx library` `import` `networkx as nx` ` ` `# create a cubical empty graph` `G ` `=` `nx.cubical_graph()` ` ` `# plotting the graph` `plt.subplot(` `122` `)` ` ` `# draw a graph with red ` `# node and vlue edge color` `nx.draw(G, pos ` `=` `nx.circular_layout(G), ` ` ` `node_color ` `=` `'r'` `,` ` ` `edge_color ` `=` `'b'` `)` |

**Output:**

**Graph Edge Removal:**

To remove an edge from the graph, use the **remove_edge() **method of graph object.

Syntax:G.remove_edge(u, v)

Parameters:

u:first node

v:second node

Return: None

**Graph Node Removal:**

To remove a node from the graph, use the **remove_node() **method of graph object.

Syntax:G.remove_node(u)

Parameter:Node to remove

Return:None

#### Show the Adjacent vertices:

## Python3

`# import networkx library` `import` `netwokx as nx` ` ` `# create an empty undirected graph` `G ` `=` `nx.Graph()` ` ` `# add edge to the graph` `G.add_edge(` `'1'` `, ` `'2'` `)` `G.add_edge(` `'2'` `, ` `'3'` `)` ` ` `# print the adjacent vertices` `print` `(G.adj)` |

**Output:**

{'1': {'2': {}}, '2': {'1': {}, '3': {}}, '3': {'2': {}}}

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