### Introduction

*Matplotlib* is one of the most widely used data visualization libraries in Python. Much of Matplotlib's popularity comes from its customization options - you can tweak just about any element from its *hierarchy of objects*.

In this tutorial, we'll take a look at how to *change the font size in Matplotlib*.

### Change Font Size in Matplotlib

There are a few ways you can go about changing the size of fonts in Matplotlib. You can set the `fontsize`

argument, change how Matplotlib treats fonts in general, or even changing the figure size.

Let's first create a simple plot that we'll want to change the size of fonts on:

```
import matplotlib.pyplot as plt
import numpy as np
fig, ax = plt.subplots(figsize=(12, 6))
x = np.arange(0, 10, 0.1)
y = np.sin(x)
z = np.cos(x)
ax.plot(y, color='blue', label='Sine wave')
ax.plot(z, color='black', label='Cosine wave')
ax.set_title('Sine and cosine waves')
ax.set_xlabel('Time')
ax.set_ylabel('Intensity')
leg = ax.legend()
plt.show()
```

#### Change Font Size using *fontsize*

Let's try out the simplest option. Every function that deals with text, such as `Title`

, labels and all other textual functions accept an argument - `fontsize`

.

Let's revisit the code from before and specify a `fontsize`

for these elements:

```
import matplotlib.pyplot as plt
import numpy as np
fig, ax = plt.subplots(figsize=(12, 6))
x = np.arange(0, 10, 0.1)
y = np.sin(x)
z = np.cos(x)
ax.plot(y, color='blue', label='Sine wave')
ax.plot(z, color='black', label='Cosine wave')
ax.set_title('Sine and cosine waves', fontsize=20)
ax.set_xlabel('Time', fontsize=16)
ax.set_ylabel('Intensity', fontsize=16)
leg = ax.legend()
plt.show()
```

Here, we've set the `fontsize`

for the title as well as the labels for time and intensity. Running this code yields:

We can also change the size of the font in the legend by adding the `prop`

argument and setting the font size there:

```
leg = ax.legend(prop={"size":16})
```

This will change the font size, which in this case also moves the legend to the bottom left so it doesn't overlap with the elements on the top right:

However, while we can set each font size like this, if we have many textual elements, and just want a uniform, general size - this approach is repetitive.

In such cases, we can turn to setting the font size *globally*.

#### Change Font Size Globally

There are two ways we can set the font size globally. We'll want to set the `font_size`

parameter to a new size. We can get to this parameter via `rcParams['font.size']`

.

One way is to modify them directly:

```
import matplotlib.pyplot as plt
import numpy as np
fig, ax = plt.subplots(figsize=(12, 6))
x = np.arange(0, 10, 0.1)
y = np.sin(x)
z = np.cos(x)
plt.rcParams['font.size'] = '16'
ax.plot(y, color='blue', label='Sine wave')
ax.plot(z, color='black', label='Cosine wave')
plt.xlabel('Time')
plt.ylabel('Intensity')
fig.suptitle('Sine and cosine waves')
leg = ax.legend()
plt.show()
```

You have to set these *before* the `plot()`

function call since if you try to apply them afterwards, no change will be made. This approach will change everything that's specified as a font by the `font`

kwargs object.

However, when we run this code, it's obvious that the x and y ticks, nor the x and y labels didn't change in size:

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Depending on the Matplotlib version you're running, you won't be able to change these with rc parameters. You'd use `axes.labelsize`

and `xtick.labelsize`

/`ytick.labelsize`

for them respectively.

If setting these doesn't change the size of labels, you can use the `set()`

function passing in a `fontsize`

or use the `set_fontsize()`

function:

```
import matplotlib.pyplot as plt
import numpy as np
fig, ax = plt.subplots(figsize=(12, 6))
x = np.arange(0, 10, 0.1)
y = np.sin(x)
z = np.cos(x)
# Set general font size
plt.rcParams['font.size'] = '16'
# Set tick font size
for label in (ax.get_xticklabels() + ax.get_yticklabels()):
label.set_fontsize(16)
ax.plot(y, color='blue', label='Sine wave')
ax.plot(z, color='black', label='Cosine wave')
plt.xlabel('Time', fontsize=16)
plt.ylabel('Intensity', fontsize=16)
fig.suptitle('Sine and cosine waves')
leg = ax.legend()
plt.show()
```

This results in:

### Conclusion

In this tutorial, we've gone over several ways to change the size of fonts in Matplotlib.

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