how can i make the input work with my parameters? - function

Question

I have started a python class and my book does not seem to help me.
My professor has a program that bombards my code with different inputs and if any of the inputs do not work then my code is "wrong". I have done many days worth of editing and am at a complete loss. I have the code working if someone puts and input of an actual number. But where my code fails the test is if input is "miles_to_laps(26)" it errors out.
I have tried changing the input to int(input()) but that does not fix the issue. I've gone through changing variables and even changing the input method but still am at a loss. I have already tried contacting my teacher but 6 days of no response and 3 days of being late i feel like I'm just going no where.
user_miles = int(input())
def miles_to_laps(user_miles):
x = user_miles
y = 4
x2 = x * y
result = print('%0.2f' % float(x2))
return result
miles_to_laps(user_miles)
my code works for real number inputs but my professor is wanting inputs like
miles_to_laps(26) and miles_to_laps(13) to create the same outputs.

Answer 1

For the wierd input functionality you can try:
import re
def parse_function_text(s):
try:
return re.search("miles_to_laps\((.+)\)", s)[1]
except TypeError:
return None
def accept_input(user_input):
desugar = parse_function_text(user_input)
if desugar is not None:
user_input = desugar
try:
return float(user_input)
except ValueError:
raise ValueError("Cannot process input %s" % user_input)
assert accept_input("miles_to_laps(3.5)") == 3.5

Answer 2

I'm trying to keep all the pedantism aside, but what kind of CS/programming teaching is that?
Areas of concern:
separate user input from rest of code
separate output formatting from function output
the code inside miles_to_laps is excessive
Now here is the code to try:
LAPS_PER_MILE = 4
# the only calculation, "pure" function
def miles_to_laps(miles):
return LAPS_PER_MILE * miles
# sorting out valid vs invalid input, "interface"
def accept_input(user_input):
try:
return float(user_input)
except ValueError:
raise ValueError("Cannot process input %s" % user_input)
if __name__ == "__main__":
# running the program
laps = miles_to_laps(accept_input(input()))
print ('%0.2f' % laps)
Hope this is not too overwhelming.
Update: second attempt
MILE = 1609.34 # meters per mile
LAP = 400 # track lap
LAPS_PER_MILE = MILE/LAP
def miles_to_laps(miles):
return LAPS_PER_MILE * miles
def laps_coerced(laps):
return '%0.2f' % laps
def accept_input(user_input):
try:
return float(user_input)
except ValueError:
raise ValueError("Cannot process input %s" % user_input)
def main(user_input_str):
miles = accept_input(user_input_str)
laps = miles_to_laps(miles)
print (laps_coerced(laps))
if __name__ == "__main__":
main(input())