Comparing in lists in Python

Question

So for my program I have two definitions, get_codes and get_data, that I created 8 total lists from, shown below:

CountryCodes=open("CountryCodes.csv",'r')
CountryData=open("CountryData.csv", 'r')

def get_codes(file):
    country_code=[]
    country_name=[]
    continent=[]

    for line in CountryCodes: 
        c_fields=line.split(",")

        c_field1=c_fields[0].strip()
        c_field2=c_fields[1].strip()
        c_field3=c_fields[2].strip() 

        country_code.append(c_field1)
        country_name.append(c_field2)
        continent.append(c_field3)

    return country_code, country_name, continent

def get_data(file): 
    data_country_code=[]
    country_pop=[]
    country_area=[]
    country_gdp=[]
    country_lit_rate=[]

    for line in CountryData: 
        d_fields=line.split(",")

        d_field1=d_fields[0].strip()
        d_field2=d_fields[1].strip()
        d_field3=d_fields[2].strip()
        d_field4=d_fields[3].strip()
        d_field5=d_fields[4].strip()

        data_country_code.append(d_field1)
        country_pop.append(int(d_field2))
        country_area.append(d_field3)
        country_gdp.append(int(d_field4))
        country_lit_rate.append(d_field5)

    return data_country_code, country_pop, country_area, country_gdp, country_lit_rate

Now what I have to do is create a menu option (I have the menu) that gives the country_pop in ascending, and later descending, order. Here's what I have so far:

def asc_sort():
    for x in range (0,len(country_pop)):
        country_pop2=sorted(country_pop)

I have the sorting down, but my professor doesn't only want the country_pop2 printed. She also wants the country_name, which is in CountryCodes, not CountryData where the population is. So the country_pop's index, x, should also be x in data_country_code. I then need to take the input of x in data_country_code, let's say it's AL, and find that in country_code. Next I'll have to find the corresponding country_name, Albania, to the country_code, AL and list the country_name with the country_pop which I assume would be something like:

print("%-10s \t %-10s \t" %("NAMES","POPULATION"))
for ind in range (0,len(list1)):
    if ind%10==9:
        input("Press ENTER to continue")
    print("%-2s \t %-10s \t %-10s \t %-10s \t %-10s \t" %(I'd need help here)

(I need the %-10s part for formatting and the if statement because my list is so long I only want a few to show at a time) Any help would be appreciated, and if anyone needs more explaining I'll do my best!

Hmm the way this question is written out now you're unlikely to get much help.. try reading about SSCCEs and modify your question accordingly. e.g., instead of giving us code that reads files, give us code that uses strings and reads from them — Claudiu
– Claudiu, Commented Oct 1, 2013 at 20:24
Hello. Are you sure that codes of countries (country_code) need to be splitted ? — eyquem
– eyquem, Commented Oct 1, 2013 at 21:15
Your way of doing isn't good. Each line of the CountryData.csv file contains the data pertaining to ONE country. What your algorithm does is to separate the data of one country into DIFFERENT lists, then you have problems to gather the data ! - It's the same fault concerning the code and the name of each country: you separate them. What you must do is to keep a link between a code and the corresponding name: that is done using a dictionary. — eyquem
– eyquem, Commented Oct 1, 2013 at 21:30
Claudiu, the information in the file lists hundreds of countries and there's so much going on with the program already I was nervous to change things up, but thanks for the input! — I am Harlie
– I am Harlie, Commented Oct 2, 2013 at 2:12
I'm not going to do your homework for you, but I can tell you that this exercise will be a lot easier if you read up on Python's CSV module. — johnsyweb
– johnsyweb, Commented Oct 2, 2013 at 9:52

Community · Accepted Answer · 2020-06-20 09:12:55Z

2

I think the following code does what you want:

with open("CountryCodes.csv",'r') as CountryCodes:
    genc = (line.split(',') for line in CountryCodes)

    c2n = dict((c_fields[0].strip(),c_fields[1].strip())
               for c_fields in genc)

with open("CountryData.csv",'r') as CountryData:
    gend = (line.split(',') for line in CountryData)

    the_data = [ (c2n[d_fields[0].strip()], # data_country_code
                  int(d_fields[1]),         # country_pop
                  d_fields[2].strip(),      # country_area
                  d_fields[3].strip(),      # country_gdp
                  d_fields[4].strip())      # country_lit_rate
                 for d_fields in gend ]

the_data.sort(key = lambda x: x[1])

p = 10
for i in xrange(0,len(the_data),p):
    if i:  raw_input("  Press ENTER to continue\n")
    print ('\n'.join("%-10s \t %-10s \t %-10s \t %-10s \t %s"
                     % el for el in the_data[i:i+p]) )

The dictionary c2n gives the names corresponding to codes.

The population field is certainly a string expressing an integer that doesn't need to be striped, even if there are whitespaces in it (blanks, tabs... not newlines)

.

EDIT

If you're not authorized to use a dictionary but only lists, you cab do like that:

with open("CountryCodes.csv",'r') as CountryCodes:
    genc = (line.split(',') for line in CountryCodes)
    lic = [map(str.strip,row) for row in genc]

def name_of(x,lic=lic):
  for code,name,continent in lic:
    if x==code:
      return name

with open("CountryData.csv",'r') as CountryData:
    gend = (line.split(',') for line in CountryData)

    the_data = [ (name_of(d_fields[0].strip()), # data_country_code
                  int(d_fields[1]),         # country_pop
                  d_fields[2].strip(),      # country_area
                  d_fields[3].strip(),      # country_gdp
                  d_fields[4].strip())      # country_lit_rate
                 for d_fields in gend ]

edited Jun 20, 2020 at 9:12

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answered Oct 1, 2013 at 22:30

eyquem

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6 Comments

I am Harlie Over a year ago

By split do you mean strip? I used strip originally because the files do have all kinds of crazy spaces in them. I'm running into an error though at the print, pardon my stupidity if this is something I was supposed to know to change but I get the error 'TypeError: Not enough arguments for format string' at the while loop. I assume this is talking about the % el for el. Any ideas?

eyquem Over a year ago

I wonder where was my brain when I did a confusion between strip and split. You are right. - Concerning the error, you would have found the reason by printing the_data, you would have seen it wasn't what was expected and that I had written CountryCodes instead of CountryData in the definition of the generator gend - I changed the code for the loop, a for-loop instead of a while-loop.

I am Harlie Over a year ago

Eyquem, your code works when separated from the rest of mine. I'm just having trouble merging it with mine but I'll figure it out. Thank you for you help!

eyquem Over a year ago

The rest of your code is probably as poorly organised as the code in your question was and trying to incorporate my code in it reveals this fact. I think you would benefit from asking help for the rest of your code too - By the way, why do you think my answer doesn't deserve to be accepted too ?

eyquem Over a year ago

@I am Harlie Thank you for your accept. How goes the rest of your code ? - I upvoted your question because of being relatively well exposed

|

andrew cooke · Accepted Answer · 2013-10-01 21:25:39Z

2

you need to do two things:

store all the data in a line from CountryData in a tuple, rather than separate lists. that way, when you rearrange everything in your sort, you also rearrange the county codes.
store the data from CountryCodes in a dict, so that you can go from code to country name.

i'm not sure i should be doing all your homework for you, but if you have data like this:

country_data = [('uk', 123), ('usa', 42), ('cl', 99)]
country_names = {'uk': 'united kingdom', 'usa': 'united states', 'cl': 'chile'}

then this would give you the country names ordered by the numbers:

sorted_data = sorted(country_data, key=lambda data: data[1])
for (code, value) in sorted_data:
    print(country_names[code], value)

note how the key picks out the second element of the tuple to sort. so, for ('uk', 123) it will give 123, which is what you want to sort by.

answered Oct 1, 2013 at 21:25

andrew cooke

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2 Comments

eyquem Over a year ago

Hello. I hadn't seen your answer when I posted my comment !

I am Harlie Over a year ago

Thank you Andrew, I've put my data into a tuple and dict like you suggested, my professor hadn't introduced either of those to us so it was a huge help!

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