This is an example for the displaytools extension for the IPython Notebook.

The extension introduces some "magic" comments (like ## and ##: ) which trigger additional output (normally only the return value of the last line of a cell is printed). See Why is this useful?



In [17]:

    
%load_ext displaytools3
%reload_ext displaytools3









    



The displaytools3 extension is already loaded. To reload it, use:
  %reload_ext displaytools3



In [18]:

    
import sympy as sp
from sympy import sin, cos
from sympy.abc import t, pi



In [19]:

    
x = 2*pi*t
y1 = cos(x)
y2 = cos(x)*t
ydot1 = y1.diff(t) ##
ydot2 = y2.diff(t) ##
ydot1_obj = y1.diff(t, evaluate=False) ##









    





$$- 2 \pi \sin{\left (2 \pi t \right )}$$






    



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$$- 2 \pi t \sin{\left (2 \pi t \right )} + \cos{\left (2 \pi t \right )}$$






    



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$$\frac{\partial}{\partial t} \cos{\left (2 \pi t \right )}$$






    



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Note that the equation sign (i.e., =) must be enclosed by two spaces, i.e.: lhs = rhs.

If the variable name is also desired this can be triggered by ##:



In [20]:

    
ydot1 = y1.diff(t) ##:
ydot2 = y2.diff(t) ##:
ydot1_obj = y1.diff(t, evaluate=False) ##:









    





$$\texttt{ydot1} := - 2 \pi \sin{\left (2 \pi t \right )}$$






    



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$$\texttt{ydot2} := - 2 \pi t \sin{\left (2 \pi t \right )} + \cos{\left (2 \pi t \right )}$$






    



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$$\texttt{ydot1_obj} := \frac{\partial}{\partial t} \cos{\left (2 \pi t \right )}$$






    



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Printing can be combined with LaTeX rendering:



In [21]:

    
sp.interactive.printing.init_printing(1)



In [22]:

    
ydot1 = y1.diff(t) ##:
ydot2 = y2.diff(t) ##:
ydot1_obj = y1.diff(t, evaluate=False) ##:









    





$$\texttt{ydot1} := - 2 \pi \sin{\left (2 \pi t \right )}$$






    



---






    





$$\texttt{ydot2} := - 2 \pi t \sin{\left (2 \pi t \right )} + \cos{\left (2 \pi t \right )}$$






    



---






    





$$\texttt{ydot1_obj} := \frac{\partial}{\partial t} \cos{\left (2 \pi t \right )}$$






    



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If there is no assignment taking place, ## nevertheless causes the display of the respective result.



In [23]:

    
y1.diff(t,t) ##
y2.diff(t,t) ##









    





$$- 4 \pi^{2} \cos{\left (2 \pi t \right )}$$






    



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$$- 4 \pi \left(\pi t \cos{\left (2 \pi t \right )} + \sin{\left (2 \pi t \right )}\right)$$






    



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Transposition

Sometimes, it can save much space if some return value is displayed in transposed form (while still being assigned not transposed). Compare these examples:



In [24]:

    
xx = sp.Matrix(sp.symbols('x1:11')) ##
yy = sp.Matrix(sp.symbols('y1:11')) ##:T

xx.shape, yy.shape ##









    





$$\left[\begin{matrix}x_{1}\\x_{2}\\x_{3}\\x_{4}\\x_{5}\\x_{6}\\x_{7}\\x_{8}\\x_{9}\\x_{10}\end{matrix}\right]$$






    



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$$\texttt{yy.T} := \left[\begin{matrix}y_{1} & y_{2} & y_{3} & y_{4} & y_{5} & y_{6} & y_{7} & y_{8} & y_{9} & y_{10}\end{matrix}\right]$$






    



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$$\left ( 10, \quad 1\right )$$






    





$$\left ( 10, \quad 1\right )$$






    



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In [25]:

    
# combination with other comments
a = 3 # comment ##:









    





$$\texttt{a} := 3$$






    



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In [28]:

    
# Multiline statements and indended lines are not yet supported:
a = [1, 
     2] ##:

if 1:
    b = [10, 20] ##:


c = [100, 200] ##:









    





$$\texttt{c} := \left [ 100, \quad 200\right ]$$






    



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Why this extension might be useful?

It saves space in the final document, when intermediate results shall be displayed (e.g. for didactic purpose)
- allows to focus more on the content/results instead of boilerplate printing code
It saves typing effort during the development process (when internal information is of interest to understand and debug the code)