Quick assistance with simple python(Learning Lists)

Question

I was learning how to use loops and was doing this program for practice. However, the only thing I am having some difficulty with is printing the list only once for each input correctly. Here is my code:

country_list=[]
emission_list=[]
capita_list=[]
total=0
end_loop=False
together=[]
while True:
 country=raw_input("Enter country or (done to end): ")
 if country=="done":
 break
 else:
 emission=input("Enter emissions: ")
 capita=input("Enter capita: ")
 country_list.append(country)
 emission_list.append(emission)
 capita_list.append(capita)
 total+=1
for x in range(len(country_list)):
 for y in range(len(emission_list)):
 for z in range(len(capita_list)):
 end_loop=True
 print country_list[x]+": Emission="+str(emission_list[y]),"and Capita="+str(capita_list[z]) 

I am inputting this:

Enter country or (done to end): Testcase
Enter emissions: 1
Enter capita: 2
Enter country or (done to end): Testcase2
Enter emissions: 3
Enter capita: 4
Enter country or (done to end): done 

This is the output I am getting:

Testcase: Emission=1 and Capita=2
Testcase: Emission=1 and Capita=4
Testcase: Emission=3 and Capita=2
Testcase: Emission=3 and Capita=4
Testcase2: Emission=1 and Capita=2
Testcase2: Emission=1 and Capita=4
Testcase2: Emission=3 and Capita=2
Testcase2: Emission=3 and Capita=4 

It is printing all possible combinations of the emissions and capita but I only want it to print what I inputted as emissions/capita for each country. Anyone know how to fix this?

Answer 1

This is ok as a learning exercise, but the Pythonic way to perform this task is to use zip.

for cnty, em, cap in zip(country_list, emission_list, capita_list):
 print "{}: Emission={} and Capita={}".format(cnty, em, cap)

Actually you should store the results that way (a list of 3-tuples) instead of with three lists that you zip together later.

cecs = []
while True:
 country = raw_input("Enter country (or nothing to end): ").strip()
 if not country:
 break
 emission = input("Enter emissions: ").strip()
 capita = input("Enter capita: ").strip()
 cecs.append((country, emission, capita))
# total = len(cecs)
for cec in cecs:
 print "{}: Emission={} and Capita={}".format(*cec)

Answer 2

Instead of doing this:

for x in range(len(country_list)):
 for y in range(len(emission_list)):
 for z in range(len(capita_list)):
 print country_list[x]+": Emission="+str(emission_list[y]),"and Capita="+str(capita_list[z])

Do this:

for x in range(len(country_list)):
 print country_list[x]+": Emission="+str(emission_list[x]),"and Capita="+str(capita_list[x])

Note: Your code will be more meaningfully structured if you create a class that has one country name, one emission and one capita. Then a mistake like this would be impossible since you'd only have one list of objects to iterate over, anyway.

• Drake Walter: Also, do you know how I can add together all the emissions for all the countries I inputted?

Answer 3

I'd rather use a dictionary instead. It'd look like something like this:

countries = {}
while True:
 inp = input("Enter country or (done to end): ")
 if inp == 'done':
 break;
 countries[inp] = {'emission': input("Enter emissions: ")}
 countries[inp]['capita'] = input("Enter capita: ")
for i in countries:
 print(i, 'Emission:', countries[i]['emission'],
 'and Capita', countries[i]['capita'])

Input:

Enter country or (done to end): test
Enter emissions: 1
Enter capita: 2
Enter country or (done to end): test2
Enter emissions: 3
Enter capita: 4
Enter country or (done to end): done

Ouput:

test Emission: 1 and Capita 2
test2 Emission: 3 and Capita 4

At the end the dictionary looks like that:

{'test': {'emission': '1', 'capita': '2'}, 'test2': {'emission': '3', 'capita': '4'}}