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Concepts

Tip

View list of currently running notebooks or labs along with the corresponding tokens

  • jupyter notebook list
  • jupyter labs list

Magic Commands

  • Can be used by default without the percent sign
    • as long as no variable is defined with the same name as the magic function in question
    • This feature is called automagic and can be enabled or disabled with %automagic
Useful Magic Commands
Command Description
%cpaste Open a special prompt for manually pasting Python code to be executed
%debug Enter the interactive debugger at the bottom of the last exception traceback
%hist Print command input (and optionally output) history
%load FILENAME Loads the file in the current cell
%magic Display detailed documentation for all of the available magic commands
%page OBJECT Pretty-print the object and display it through a pager
%paste Execute preformatted Python code from clipboard
%pdb Automatically enter debugger after any exception
%prunstatement Execute statement with cProfile and report the profiler output
%quickref Display the IPython Quick Reference Card
%reset Delete all variables/names defined in interactive namespace
%runscript.py Run a Python script inside IPython
%%timeit Calc time taken to run a python code snippet
%timeitstatement Run a statement multiple times to compute an ensemble average execution time; useful for timing code with very short execution time
%timestatement Report the execution time of a single statement
%who, %who_ls, %whos Display variables defined in interactive namespace, with varying levels of information/verbosity
%xdelvariable Delete a variable and attempt to clear any references to the object in the IPython internals

Widgets

Tip

If the widgets don't display correctly, follow the steps here to ensure all relevant libraries are installed.

Interact

  • Passing a function with an integer or float argument or range to interact creates a slider
  • Default step size is 1 for integers and 0.1 for floats
  • When specifying min and max or min, max and step as the widget arguments, the default value can be set in the function definition
  • We can also specify the min, max, step and default in the function itself
    • Interact can be called just with the function name in this case
    • When used as a decorator, no parameters are needed in this case

Usage

# Without specifying min, max, step and default in the function
# Create a slider
interact(function_name, x=intval) 
interact(function_name, x=(min,max)) 
interact(function_name, x=(min,max,step)) 
# The above invokes the IntSlider widget in the following form
interact(function_name, x=widgets.IntSlider(min=-intval,max=3 * intval,step=1,value=intval))

# With min, max, step and default specified in the function
# Create a slider
interact(function_name)
Sample Code 
from ipywidgets import interact, fixed, interact_manual
import ipywidgets as widgets

# Sample function
def f(x):
    return x

# Slider
interact(f, x=10) 

# Specify min, max, step and val for the slider explicitly
interact(f, x=widgets.IntSlider(min=-100,max=100,step=5,value=0))

# Checkbox
interact(f, x=True)

# Textarea
interact(f, x='Hello')

# Dropdown
interact(f, x=['listval1','listval2'])

# Dropdown - displays dict key in dropdown and return value corresponding to selection
interact(f, x={'key1':val1,'key2':val2})



# Sample function with default value
def g(x=14):
    return x

# Specify min and max for the slider explicitly
interact(g, x=(10,15)) 
# Specify min, max and step for the slider explicitly
interact(g, x=(10,20,2)) 

# Sample function with min, max, step and default values
def g1(x=14):  # same as def g1(x:14)
    return x
def g1(x=(10,20)):  # same as def g1(x:(10,20))
    return x
def g1(x=(10,20,2)):  # same as def g1(x:(10,20,2))
    return x
def g1(x=widgets.IntSlider(min=-100,max=100,step=5,value=0)):  # same as def g1(x:idgets.IntSlider(min=-100,max=100,step=5,value=0))
    return x

interact(g1)
Using interact as decorator 
# function name is not passed as argument when using interact as a decorator
@interact
def f(x:10):
    return x

@interact(x=widgets.IntSlider(min=-100,max=100,step=5,value=0))
def f(x):
    return x

@interact
def f(x:widgets.IntSlider(min=-100,max=100,step=5,value=0)):
    return x

The function fixed can be used to fix the value of arguments. 

# Here even though there are two arguments, only one interactive widget is displayed
@interact
def f(x=5, y=fixed(10)):
    return (x,y)

Interactive

  • Used if there is a need to reuse the widgets
  • Returns a Widget instance rather than immediately displaying the widget
    • Use IPython's display function to display the widget
from ipywidgets import interactive, fixed
import ipywidgets as widgets
from IPython.display import display

def f(x:widgets.IntSlider(min=-100,max=100,step=5,value=0), y:10):
    return (x,y)

w = interactive(f)

# Display the widget(s)
display(w)

# Print the widgets being used
w.children
# Returns
# (IntSlider(value=0, description='x', min=-100, step=5),
#  IntSlider(value=10, description='y', max=30, min=-10),
#  Output())

# Get the results
# Rerun this after every interaction with the widgets
w.result 
# Returns (0, 10)

# Get the arguments and values as a dict
w.kwargs
# Returns {'x': 0, 'y': 10}

# Close the widget
w.close()

# Once the widget is closed, display return the text representation of the widget
display(w)
# returns interactive(children=(IntSlider(value=0, description='x', min=-100, step=5), IntSlider(value=10, description='y', max=30, min=-10), Output()), _dom_classes=('widget-interact',))
# w.children, w.result and w.kwargs return the normal outputs

Standalone Widgets

  • Displayed using the display() method
  • Values are accessed using the value property
import ipywidgets as widgets
from IPython.display import display

# Create an integer slider
w = widgets.IntSlider()
# Create a float slider
w = widgets.FloatSlider()
# Create acheckbox
w = widgets.Checkbox()
# Create a text widget
w = widgets.Text()
# Create a textarea
w = widgets.Textarea()

# Display the widget
display(w)
# Interact with the widgets and access the value using the value property
w.value

# Pass disabled parameter or set disabled property to False to disable the widget
w = widgets.IntSlider(disabled=False)
# Enable the widget
w.disabled = False

# Initialize with default value
w = widgets.Text(value='Hello', disabled=True)

# View the full list of available properties
w.keys

# Linking widgets - Cannot link more than two widgets at a time
a = widgets.FloatText()    # widgets.Text() also works
b = widgets.FloatSlider()
display(a,b)

widgetlink = widgets.jslink((a, 'value'), (b, 'value'))

# Unlinking widgets
widgetlink.unlink()