Functions And Software Development Workflow

Some key concepts

Function signature: its name, inputs, and outputs
Use notebooks for (a) exploratory development and (b) results presentation. Don't use notebooks to contain significant code.
To use a function inside a notebook, you must import its containint module.

Iterative development of a function

Construct a function that tests if a number is prime.



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5 / 3



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5 % 3



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import numpy as np
value = 4
is_prime = True
upper = int(np.ceil(np.sqrt(value)))
for divisor in range(2, upper+1):
    if value % divisor == 0:
        is_prime = False
        break
print(is_prime)



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value = 4
def isPrime(value):
    is_prime = True
    upper = int(np.ceil(np.sqrt(value)))
    if value == 2:  # THIS IS TERRIBLE
        return is_prime
    for divisor in range(2, upper+1):
        if value % divisor == 0:
            is_prime = False
            break
    return is_prime



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for val in range(2, 20):
    print("%d: %d" % (val, isPrime(val)))

Put the function in a python module



In [2]:

    
import is_prime
is_prime.isPrime(4)









    Out[2]:





False



In [4]:

    
for val in range(2, 20):
    print("%d: %d" % (val, is_prime.isPrime(val)))

Use the function in a function

Write a function that lists the prime numbers less than a threshold.

Exercise: Put this new function into a different python module and call it from the notebook.