I have a python code to generate a random graph of 300 nodes and 200 edges and display it

import networkx as nx
import matplotlib.pyplot as pltG = nx.gnm_random_graph(300,200)
graph_pos = nx.spring_layout(G)
nx.draw_networkx_nodes(G, graph_pos, node_size=10, node_color='blue', alpha=0.3)
nx.draw_networkx_edges(G, graph_pos)
nx.draw_networkx_labels(G, graph_pos, font_size=8, font_family='sans-serif')
plt.show()

However, because there are too many nodes , I need to have more pixels so that I can zoom in and save it.

If I put

plt.figure(figsize=(18,18))

before showing, then the nodes and edges don't appear. What is the problem and How do I fix this?

The plot window uses screen resolution and you can zoom it without loss of information. If you put a figure just before showing it the only thing that should happen is that two windows will appear (because you already have one figure working). So if you want to customize figure size just do it before populating your plot:

import networkx as nx
import matplotlib.pyplot as pltplt.figure(figsize=(18,18))G = nx.gnm_random_graph(300,200)
graph_pos = nx.spring_layout(G)
nx.draw_networkx_nodes(G, graph_pos, node_size=10, node_color='blue', alpha=0.3)
nx.draw_networkx_edges(G, graph_pos)
nx.draw_networkx_labels(G, graph_pos, font_size=8, font_family='sans-serif')plt.show()

To have an image (here resolution is important) that you can zoom and avoid seeing big pixels you can either:

plt.savefig("plot.png", dpi=1000)

, saving a png with a very large dpi. Or:

plt.savefig("plot.pdf")

, which will save the plot as vector graphic (into pdf). Matplotlib plot window has a tool which allows you to zoom in to any part of the plot: