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"""
=======
Textbox
=======
The Textbox widget lets users interactively provide text input, including
formulas. In this example, the plot is updated using the `.on_submit` method.
This method triggers the execution of the *submit* function when the
user presses enter in the textbox or leaves the textbox.
Note: The `matplotlib.widgets.TextBox` widget is different from the following
static elements: :ref:`annotations` and
:doc:`/gallery/text_labels_and_annotations/placing_text_boxes`.
"""
import matplotlib.pyplot as plt
import numpy as np
from matplotlib.widgets import TextBox
fig, ax = plt.subplots()
fig.subplots_adjust(bottom=0.2)
t = np.arange(-2.0, 2.0, 0.001)
l, = ax.plot(t, np.zeros_like(t), lw=2)
def submit(expression):
"""
Update the plotted function to the new math *expression*.
*expression* is a string using "t" as its independent variable, e.g.
"t ** 3".
"""
ydata = eval(expression, {'np': np}, {'t': t})
l.set_ydata(ydata)
ax.relim()
ax.autoscale_view()
plt.draw()
axbox = fig.add_axes([0.1, 0.05, 0.8, 0.075])
text_box = TextBox(axbox, "Evaluate", textalignment="center")
text_box.on_submit(submit)
text_box.set_val("t ** 2") # Trigger `submit` with the initial string.
plt.show()
# %%
#
# .. admonition:: References
#
# The use of the following functions, methods, classes and modules is shown
# in this example:
#
# - `matplotlib.widgets.TextBox`
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