Basic plt.plot usage in Matplotlib - Step-by-Step Execution

Concept Flow - Basic plt.plot usage

Import matplotlib.pyplot as plt

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Prepare data: x and y lists

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Call plt.plot(x, y)

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Plot line graph appears

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Call plt.show() to display plot

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Graph window opens

This flow shows how to import matplotlib, prepare data, plot it using plt.plot, and display the graph.

Execution Sample

Matplotlib

import matplotlib.pyplot as plt
x = [1, 2, 3, 4]
y = [10, 20, 25, 30]
plt.plot(x, y)
plt.show()

This code plots points (1,10), (2,20), (3,25), (4,30) connected by lines and shows the graph.

Execution Table

Step	Action	Data State	Plot State	Output
1	Import matplotlib.pyplot as plt	No data yet	No plot	Module loaded
2	Create x = [1, 2, 3, 4]	x = [1, 2, 3, 4]	No plot	List x created
3	Create y = [10, 20, 25, 30]	y = [10, 20, 25, 30]	No plot	List y created
4	Call plt.plot(x, y)	x and y unchanged	Line plot prepared	Plot line connecting points
5	Call plt.show()	Data unchanged	Plot displayed	Graph window opens showing line plot

💡 Plot displayed and program waits until window is closed

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
x	undefined	[1, 2, 3, 4]	[1, 2, 3, 4]	[1, 2, 3, 4]
y	undefined	undefined	[10, 20, 25, 30]	[10, 20, 25, 30]

Key Moments - 2 Insights

Why do we need to call plt.show() after plt.plot()?

plt.plot() prepares the plot but does not display it. plt.show() opens the window to display the graph, as shown in execution_table step 5.

What happens if x and y lists have different lengths?

Matplotlib will raise an error because it needs matching x and y points to plot lines. This is not shown here but is important to keep lists equal length.

Visual Quiz - 3 Questions

Look at the execution table, what is the state of the plot after step 4?

A Line plot prepared connecting points

B No plot prepared yet

C Plot displayed on screen

D Plot data cleared

💡 Hint

Check the 'Plot State' column at step 4 in the execution_table

At which step does the graph window open to show the plot?

A Step 2

B Step 3

C Step 5

D Step 4

💡 Hint

Look at the 'Output' column in execution_table for when the graph window opens

If we change y to [5, 15, 20, 25], what will happen to the plot?

A The plot will not change

B The plot will show points with new y values connected by lines

C An error will occur because y changed

D The plot will show points with old y values

💡 Hint

Variable tracker shows y values affect the plot points connected by plt.plot

Concept Snapshot

Basic plt.plot usage:
- Import matplotlib.pyplot as plt
- Prepare x and y data lists
- Call plt.plot(x, y) to create line plot
- Call plt.show() to display the plot window
- x and y must be same length
- Plot connects points (x[i], y[i]) with lines

Full Transcript

This visual execution shows how to use matplotlib's plt.plot function. First, we import matplotlib.pyplot as plt. Then we create two lists x and y with numbers representing points on the x and y axes. Calling plt.plot(x, y) prepares a line plot connecting these points but does not display it yet. Finally, plt.show() opens a window showing the graph. Variables x and y hold the data points. The plot state changes from no plot to line plot prepared, then to plot displayed. Remember, plt.show() is needed to see the graph. Also, x and y must have the same length to avoid errors.