Python, metric conversion program, no dictionary

Question

I made a code which converts one measurement to another. (I'm not allowed to use dictionary) I keep getting an error message: NameError: name 'num2' is not defined, which means the if statement in the second loop never became true I guess. Still, I have no idea what went wrong.

Any ideas will be appreciated. Thanks!

# Metric conversion program

def displayWelcome():
    print('This program converts convert one length unit into another unit')
    print('Following are the available units: (mm), (cm), (m), (km), (inches), (ft), (yds), (miles)')

def getConvertfrom():
    which1 = input('Which unit would you like to convert from: ')

def getConvertto():    
    which2 = input ('Which unit would you like to convert to: ')


num1 = float(input('Enter a value: '))

available_units = ('mm', 'cm', 'm', 'km', 'inches', 'ft', 'yds', 'miles')
conversions = (1, 10, 1000, 1e6, 25.4, 304.8, 914.4, 1.609344e6)

# Display program welcome
displayWelcome()

# Get which conversion
which1 = getConvertfrom()
which2 = getConvertto()



index = 0
for i in range (0, len(available_units)):
    if available_units[i] == str(which1):
        num_in_mm = num1 * conversions[i]

for j in range (0, len(available_units)):
    if available_units[j] == str(which2):
        num2 = num_in_mm / conversions[j]

print(num1, which1, "is equal to", num2, which2)

Answer 1

This is your code with some minor changes on getting input from user (using raw_input ). Moreover return your input, in your case which1 , and which2 was None (as you were trying to set variable inside of your function scope):

# Metric conversion program

def displayWelcome():
    print('This program converts convert one length unit into another unit')
    print('Following are the available units: (mm), (cm), (m), (km), (inches), (ft), (yds), (miles)')

def getConvertfrom():
    return raw_input('Which unit would you like to convert from: ')

def getConvertto():
    return raw_input('Which unit would you like to convert to: ')


num1 = float(raw_input('Enter a value: '))

available_units = ('mm', 'cm', 'm', 'km', 'inches', 'ft', 'yds', 'miles')
conversions = (1, 10, 1000, 1e6, 25.4, 304.8, 914.4, 1.609344e6)

# Display program welcome
displayWelcome()

# Get which conversion
which1 = getConvertfrom()
which2 = getConvertto()

index = 0
for i in range (0, len(available_units)):
    print available_units[i], '==', str(which1)
    if available_units[i] == str(which1):
        num_in_mm = num1 * conversions[i]

for j in range (0, len(available_units)):
    if available_units[j] == str(which2):
        num2 = num_in_mm / conversions[j]

print(num1, which1, "is equal to", num2, which2)

This is a sample output of the script for converting mm value to cm :

$ python testtest.py
Enter a value: 1000
This program converts convert one length unit into another unit
Following are the available units: (mm), (cm), (m), (km), (inches), (ft), (yds), (miles)
Which unit would you like to convert from: mm
Which unit would you like to convert to: cm
given params: which1: mm, which2: cm
mm == mm
cm == mm
m == mm
km == mm
inches == mm
ft == mm
yds == mm
miles == mm
(1000.0, 'mm', 'is equal to', 100.0, 'cm')

NB: input is equal to eval(raw_input(prompt)) and you don't need to do that as it has other use cases and you have to embody your input string in quotes! Simply use raw_input.

Answer 2

conversions = (1, 10, 1000, 1e6, 25.4, 304.8, 914.4, 1.609344e6) regarding about this ? How I could able to do metrix = {1 : [1000, 'Kilomer'], 2: [[1],'Megameter'], 3: 'Gigameter', 4: 'Terameter', 5: 'Petameter', 6: 'Millimeter', 7: 'Micrometer', 8: 'Nanometer',9: 'Picometer', 10: 'Femtometer'}