Line Plot

When to use line plots

Line plots are best for:

• Trends over time
• Comparing changes across periods

A line plot is Matplotlib's default: plt.plot(data) alone draws a line, connecting each point to the next in the order the data appears. Points aren't interpolated by magic — Matplotlib just draws straight segments between consecutive (x, y) pairs, so ordering your data matters.

  flowchart LR
  A["x values"] --> C["plt.plot(x, y)"]
  B["y values"] --> C
  C --> D["marker + linestyle"]
  D --> E["title / xlabel / ylabel"]
  E --> F["legend (if multiple series)"]

Basic line plot

import matplotlib.pyplot as plt
 
x = [1, 2, 3, 4, 5]
y = [120, 140, 130, 160, 155]
 
plt.figure(figsize=(7, 4))
plt.plot(x, y, marker="o")
plt.title("Orders over time")
plt.xlabel("Day")
plt.ylabel("Orders")
plt.grid(True, alpha=0.3)
plt.tight_layout()
plt.show()

Multiple lines

import matplotlib.pyplot as plt
 
x = [1, 2, 3, 4, 5]
y1 = [120, 140, 130, 160, 155]
y2 = [100, 110, 120, 125, 140]
 
plt.figure(figsize=(7, 4))
plt.plot(x, y1, label="Product A")
plt.plot(x, y2, label="Product B")
 
plt.title("Orders over time")
plt.xlabel("Day")
plt.ylabel("Orders")
plt.legend()
plt.grid(True, alpha=0.3)
plt.tight_layout()
plt.show()

Visualize it

Watch a line plot draw itself point by point — each new value connects to the previous one with a straight segment:

Tip

If lines cross and the plot becomes confusing, consider faceting (multiple subplots) or focusing on fewer series.

Check your understanding

Next

Continue to Bar Chart and Horizontal Bar to compare categories instead of trends.

🧪 Try It Yourself

Exercise 1 – Plot with a marker

Press Run to see what your code prints.

Exercise 2 – Label a series for the legend

Press Run to see what your code prints.

Exercise 3 – Step drawstyle

Press Run to see what your code prints.