**Adventures in Python: User-Entry Function**

The following script allows the user to enter a function,
including math functions (math.sqrt, math.sin, etc). The function is entered as string and when calculation
is needed, the eval function is called.

Script:

# Program 010: Asking for a function - Using Eval

# To generate a
table

# allow for math
functions

import math

# ask for the
parameters

print('Generate
f(x): You can use math. functions')

print('Such as
math.sqrt, math.sin, math.exp, etc.')

print('Remember the
default angle measure is radians.')

print('Use math.pi
for \u03C0')

# f(x) and
parameters will be entered as a string

fx = input('Please
enter f(x): ')

# use float for end
marks

beg =
input('Beginning point: ')

end = input('Ending
point: ')

step = input('Step:
')

# use eval to
evaluate the parameters, turning them into floating numbers

beg = eval(beg)

end = eval(end)

step = eval(step)

print('BEGIN')

# since a floating
number with begin, end, and step may be used,

# we must use a while
loop instead of a for loop

k = beg

while k<=end:

# function evaluation

x = k

y = eval(fx)

#
print the data to six decimal places

x = round(x,6)

y = round(y,6)

print(x,',',y)

print('-----')

# use += for storage arithmetic

k += step

# end of table

print('END')

Example:

f(x) = √(x^2 + 1) from x = 0 to x = 4, step 0.5

Result:

Generate
f(x): You can use math. functions

Such as
math.sqrt, math.sin, math.exp, etc.

Remember
the default angle measure is radians.

Use
math.pi for π

Please
enter f(x): math.sqrt(x**2+1)

Beginning
point: 0

Ending
point: 4

Step: 0.5

BEGIN

0 , 1.0

-----

0.5 ,
1.118034

-----

1.0 ,
1.414214

-----

1.5 ,
1.802776

-----

2.0 ,
2.236068

-----

2.5 ,
2.692582

-----

3.0 ,
3.162278

-----

3.5 ,
3.640055

-----

4.0 ,
4.123106

-----

END

Pretty straight forward.
I hope you are enjoying this series on Python. Until next time,

Eddie

This blog is property of Edward Shore, 2017

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