How do I write a code in python that takes a user's input and assigns it to a variable, even when the user doesn't enter anything

#>>>>>>>>>WHEN VOMITING...... Apply 5C's
if 'vomiting' in Pres_Comp:
    Course_V = input('Tell me about the vomiting' +'....'+'When did the vomiting begin?')
    Cause_V = input('Any idea what might be responsible for the vomiting?')
    dete_P = False
    if 'yes' in Cause_V:
              dete_cause = input('What do you think might be responsible for causing the vomiting? ')
              if 'poison' or 'poisoning' in dete_cause:
                      dete_P = input ("Can you tell with what?")
                      det_P = 'to have been poisoned'
    if 'no' in Cause_V:
        dete_cause = False
        print()
    Complication_V1=input('Has this vomiting gotten worse over time?')
    if 'yes' in Complication_V1:
        Dete_CompV = input('Describe in a single sentence, how the vomiting has gotten worse?')
        # watery + acidic vomits + projectile vomiting? = pyloric obstruction. # greenish vomitus = upper SI obstruction. # brownish vomitus (with increasingly foul smell) = lower SI obstruction
        print('State in a single sentence, what you vomit...by completing the sentence below')
    if 'no' in Complication_V1:
            print('State in a single sentence, what you vomit...by completing the sentence below')
            print()
    Complication_V2 = input('I vomit...')
    if 'blood' in Complication_V2:
        DetHb = input('since when did you begin to notice blood in your vomit')
        Hb_Colour = [ 'Bright red blood', 'Dark red blood', 'Blood as dark as coffee']
        for x in Hb_Colour:
            print (x)
            print()
            
        DesHb_Colour = input("Which of the above, best describes the colour of blood, you noticed in your vomit?")
    
    Care_V=input('What things have you done or taken in order to stop the vomiting?')
    if 'drugs' or 'medicine' in Care_V:
        Dete_Drug0=input('Like...?')

def desv(Course_V, Complication_V2):
    return f"Vomiting is said to have begun {Course_V}, with patient vomiting {Complication_V2} "
    
while Course_V is False:
    emesis = desv(Course_V, Complication_V2)# For Px who knows when vomiting began, and characteristics of vomitus. Px has no idea what is responsible for causing vomiting.


def desv1(Course_V, dete_cause, Complication_V2):
    return f"Vomiting is said to have begun {Course_V}, patient believes {dete_cause} might be responsible for the vomiting.And vomits {Complication_V2} "

while Course_V is False:
    emesis_1 = desv1(Course_V, dete_cause, Complication_V2) 

#For Px who knows when vomiting began and has an idea of what might have elicited emesis.


def desv2(Course_V, dete_P, Complication_V2):
    return f"Vomiting is said to have begun {Course_V}, patient claims to have been poisoned with {dete_P}, and vomits {Complication_V2} "

while dete_P is False:
        emesis_2 = desv2(Course_V, dete_P, Complication_V2)

emesis_2 = desv2(Course_V, dete_P, Complication_V2)
# For Px who knows when vomiting began and believes to have been poisoned.

 #___________Pres_EMESIS
if 'no' in Cause_V and 'yes' in Complication_V1:
    print(emesis)   
           
if ('vomiting' in Pres_Comp) and ('yes' in Cause_V) and not ('poisoning' in dete_cause):
    print(emesis_1)
    
if 'vomiting' in Pres_Comp and 'poisoning' in dete_cause:
        print (emesis_2)