The focus of this notebook is refactoring a loop that

gets user input
quits if that input matches some sentinel value
processes the user input

The interesting part starts around cell #4.



In [1]:

    
from functools import partial



In [2]:

    
def convert(s):
    converters = (int, float)
    
    for converter in converters:
        try:
            value = converter(s)
        except ValueError:
            pass
        else:
            return value
        
    return s



In [3]:

    
def process_input(s):
    value = convert(s)
    print('%r becomes %r' % (s, value))

Below is a typical loop for

getting user input
quitting the loop if the user enters a special value
processing the input



In [4]:

    
def main():
    prompt = 'gimme: '
    while True:
        s = input(prompt)
        if s == 'quit':
            break
        process_input(s)

It works as shown below.



In [5]:

    
main()









    



gimme: 123.34
'123.34' becomes 123.34
gimme: 1243
'1243' becomes 1243
gimme: hello
'hello' becomes 'hello'
gimme: quit

Below is a different way of writing that loop.

How would you apply it to loop at the bottom of 2016-04/2016-Apr-Gutenberg.py?



In [6]:

    
def main():
    prompt = 'gimme: '
    for s in iter(partial(input, prompt), 'quit'):
        process_input(s)



In [7]:

    
main()









    



gimme: 123.34
'123.34' becomes 123.34
gimme: 1243
'1243' becomes 1243
gimme: hello
'hello' becomes 'hello'
gimme: quit

It can be reduced to a generator expression.



In [8]:

    
prompt = 'gimme: '
get_values = (convert(s) for s in iter(partial(input, prompt), 'quit'))
for value in get_values:
    print(value)









    



gimme: 123.34
123.34
gimme: 1243
1243
gimme: hello
hello
gimme: quit

2017-10-06 More thoughts about partial(input, prompt) and alternatives to it.



In [9]:

    
prompt = 'gimme: '

def get_input():
    return input(prompt)

def main():
    for s in iter(get_input, 'quit'):
        process_input(s)



In [10]:

    
main()









    



gimme: 123.34
'123.34' becomes 123.34
gimme: 1243
'1243' becomes 1243
gimme: hello
'hello' becomes 'hello'
gimme: quit



In [11]:

    
def main():
    prompt = 'gimme: '
    for s in iter(lambda : input(prompt), 'quit'):
        process_input(s)



In [12]:

    
main()









    



gimme: 123.34
'123.34' becomes 123.34
gimme: 1243
'1243' becomes 1243
gimme: hello
'hello' becomes 'hello'
gimme: quit



In [13]:

    
def my_partial(function, *args, **kwargs):
    def helper():
        return function(*args, **kwargs)
    return helper

def main():
    prompt = 'gimme: '
    for s in iter(my_partial(input, prompt), 'quit'):
        process_input(s)



In [14]:

    
main()









    



gimme: 123.34
'123.34' becomes 123.34
gimme: 1243
'1243' becomes 1243
gimme: hello
'hello' becomes 'hello'
gimme: quit