I need to create a function that reads the data given and creates a list that contains tuples each of which has as its first element the name of the airport and as its second and third its geographical coordinates as float numbers.
airport_data = """
Alexandroupoli 40.855869°N 25.956264°E
Athens 37.936389°N 23.947222°E
Chania 35.531667°N 24.149722°E
Chios 38.343056°N 26.140556°E
Corfu 39.601944°N 19.911667°E
Heraklion 35.339722°N 25.180278°E"""
airports = []
import re
airport_data1 = re.sub("[°N#°E]","",airport_data)
def process_airports(string):
airports_temp = list(string.split())
airports = [tuple(airports_temp[x:x+3]) for x in range(0, len(airports_temp), 3)]
return airports
print(process_airports(airport_data1))
This is my code so far but I'm new to Python, so I'm struggling to debug my code.
If you want the second and third element of the tuple to be a float, you have to convert them using the float() function.
One way to do this is creating a tuple with round brackets in your list comprehension and convert the values there:
def process_airports(string):
airports_temp = string.split()
airports = [(airports_temp[x], float(airports_temp[x+1]), float(airports_temp[x+2])) for x in range(0, len(airports_temp), 3)]
return airports
This yields a pretty unwieldy expression, so maybe this problem could be solved more readable with a classical for loop.
Also note that slpit() already returns a list.
Further remark: If you just cut off the letters from coordinates this might come back to bite you when your airports are in different quadrants.
You need to take in account N/S, W/E for longitude and latitude.
May be
def process_airports(string):
airports = []
for line in string.split('\n'):
if not line: continue
name, lon, lat = line.split()
airports.append((name,
float(lon[:-2]) * (1 if lon[-1] == "N" else -1),
float(lat[:-2]) * (-1 if lat[-1] == "E" else 1)
))
return airports
>>> process_airports(airport_data1)
[('Alexandroupoli', 40.855869, -25.956264), ('Athens', 37.936389, -23.947222), ('Chania', 35.531667, -24.149722), ('Chios', 38.343056, -26.140556), ('Corfu', 39.601944, -19.911667), ('Heraklion', 35.339722, -25.180278)]
I prefered the double split to put in evidence the differences lines/tuple elements
Related
how are you?
I'm trying to take the lowest value of the following code, my idea is that for example the result will be like. country,price,date
im using python for the code
valores= ["al[8075]['2019-05-27']", "de[2177]['2019-05-27']", "at[3946]['2019-05-27']", "be[3019]['2019-05-26']", "by[5741]['2019-05-27']", "ba[0]['2019-05-26', '2019-05-27']", "bg[3223]['2019-05-26']", "hr[4358]['2019-05-26']", "dk[5006]['2019-05-27']", "sk[4964]['2019-05-27']", "si[5253]['2019-05-26']", "es[3813]['2019-05-27']", "ee[4699]['2019-05-27']", "ru[4889]['2019-05-27']", "fi[5410]['2019-05-26']", "fr[2506]['2019-05-26']", "gi[0]['2019-05-26', '2019-05-27']", "gr[1468]['2019-05-26']", "hu[3475]['2019-05-27']", "ie[5360]['2019-05-26']", "is[0]['2019-05-26']", "it[2970]['2019-05-26']", "lv[2482]['2019-05-27']", "lt[1276]['2019-05-27']", "lu[0]['2019-05-26']", "mk[5417]['2019-05-26']", "mt[3532]['2019-05-26']", "md[6158]['2019-05-27']", "me[11080]['2019-05-26']", "no[2967]['2019-05-27']", "nl[3640]['2019-05-27']", "pl[2596]['2019-05-27']", "pt[5409]['2019-05-27']", "uk[5010]['2019-05-27']", "cz[5493]['2019-05-26']", "ro[1017]['2019-05-27']", "rs[6535]['2019-05-27']", "se[3971]['2019-05-26']", "ch[5112]['2019-05-26']", "tr[3761]['2019-05-26']", "ua[5187]['2019-05-26']"]
the idea in this example will be like
as you see country(ro) price(1017) date('2019-05-27') is the lowest
valores= "ro[1017]['2019-05-27']"
Python's max() and min() functions take a key argument. So, whenever you need a minimum or maximum you can often leverage these built-ins. The only code you have to write something to convert a value to the corresponding representation for max/min purposes.
def f(s):
return int(s.split('[')[1].split(']')[0]) or float('inf')
lowest = min(valores, key = f) # ro[1017]['2019-05-27']
There are more than one way of coding this. The following will do this:
lowest = 1000000
target = " "
for i in valores:
ix = i.find("[") + 1
iy = i.find("]")
value = int(i[ix:iy])
if value < lowest and value != 0:
lowest = value
target = i
print(target)
It will output
"ro[1017]['2019-05-27]"
However, here I am assuming you do not want 0 values, otherwise the answer would be
"ba[0]['2019-05-26', '2019-05-27']"
If you want to include 0, just modify the if block.
This should work for you. I assume you want the lowest non-zero price.
I split every string in the lists into sublists via square brackets [ and strip away the extra brackets [ and ] for each item, hence each sublist will have [state, price, dates] .
I then sort on the price, which is the second item of each sublist, and filter out the 0 prices,
The result will then be the first element of the filtered list
import re
import re
valores= ["al[8075]['2019-05-27']", "de[2177]['2019-05-27']", "at[3946]['2019-05-27']", "be[3019]['2019-05-26']", "by[5741]['2019-05-27']", "ba[0]['2019-05-26', '2019-05-27']", "bg[3223]['2019-05-26']", "hr[4358]['2019-05-26']", "dk[5006]['2019-05-27']", "sk[4964]['2019-05-27']", "si[5253]['2019-05-26']", "es[3813]['2019-05-27']", "ee[4699]['2019-05-27']", "ru[4889]['2019-05-27']", "fi[5410]['2019-05-26']", "fr[2506]['2019-05-26']", "gi[0]['2019-05-26', '2019-05-27']", "gr[1468]['2019-05-26']", "hu[3475]['2019-05-27']", "ie[5360]['2019-05-26']", "is[0]['2019-05-26']", "it[2970]['2019-05-26']", "lv[2482]['2019-05-27']", "lt[1276]['2019-05-27']", "lu[0]['2019-05-26']", "mk[5417]['2019-05-26']", "mt[3532]['2019-05-26']", "md[6158]['2019-05-27']", "me[11080]['2019-05-26']", "no[2967]['2019-05-27']", "nl[3640]['2019-05-27']", "pl[2596]['2019-05-27']", "pt[5409]['2019-05-27']", "uk[5010]['2019-05-27']", "cz[5493]['2019-05-26']", "ro[1017]['2019-05-27']", "rs[6535]['2019-05-27']", "se[3971]['2019-05-26']", "ch[5112]['2019-05-26']", "tr[3761]['2019-05-26']", "ua[5187]['2019-05-26']"]
results = []
#Iterate through valores
for item in valores:
#Extract elements from each string by splitting on [ and then stripping extra square brackets
items = [it.strip('][') for it in item.split('[')]
results.append(items)
#Sort on the second element which is price, and filter prices with are 0
res = list(
filter(lambda x: int(x[1]) > 0,
sorted(results, key=lambda x:int(x[1])))
)
#This is your lowest non-zero price
print(res[0])
The output will be
['ro', '1017', "'2019-05-27'"]
I have this list called countries.txt that list all the countries by their name, area(in km2), population (eg. ["Afghanistan", 647500.0, 25500100]).
def readCountries(filename):
result=[]
lines=open(filename)
for line in lines:
result.append(line.strip('\n').split(',\t'))
for sublist in result:
sublist[1]=float(sublist[1])
sublist[2]=int(sublist[2])
I am trying to sort through the list using a bubble sort according to the are of each country:
>> c = countryByArea(7)
>>> c
>>["India",3287590.0,1239240000]
When typing in the parameter is should return the nth largest area.
I have this but I'm not sure how to output the information
def countryByArea(area):
myList=readCountries('countries.txt')
for i in range(0,len(list)):
for j in range(0,len(list)-1):
if list[j]>list[j+1]:
temp=list[j]
list[j]=list[j+1]
list[j+1]=temp
first of all, implement a generic bubble sort method. this is a correct bubble sort algorithm implementation... Im sure you can find other implementations on http://rosettacode.org
def bubble_sort(a_list,a_key):
changed=True
while changed:
changed = False
for i in range(len(a_list)-1):
if a_key(a_list[i]) > a_key(a_list[i+1]):
a_list[i],a_list[i+1] = a_list[i+1],a_list[i]
changed = True
then simply pass a key function that represents the data you want to sort by (in this case the middle value or index one of each row
import csv
def sort_by_area(fname):
with open(fname) as f:
a = list(csv.reader(f))
bubble_sort(a,lambda row:int(row[1]))
return a
a = sort_by_area("a_file.txt")
print a[-7] #the 7th largest by area
you can take this info and combine it to complete your assignment ... but really this is a question you should have asked a classmate or your teacher for help with ...
I am new to Python and I have a hard time solving this.
I am trying to sort a list to be able to human sort it 1) by the first number and 2) the second number. I would like to have something like this:
'1-1bird'
'1-1mouse'
'1-1nmouses'
'1-2mouse'
'1-2nmouses'
'1-3bird'
'10-1birds'
(...)
Those numbers can be from 1 to 99 ex: 99-99bird is possible.
This is the code I have after a couple of headaches. Being able to then sort by the following first letter would be a bonus.
Here is what I've tried:
#!/usr/bin/python
myList = list()
myList = ['1-10bird', '1-10mouse', '1-10nmouses', '1-10person', '1-10cat', '1-11bird', '1-11mouse', '1-11nmouses', '1-11person', '1-11cat', '1-12bird', '1-12mouse', '1-12nmouses', '1-12person', '1-13mouse', '1-13nmouses', '1-13person', '1-14bird', '1-14mouse', '1-14nmouses', '1-14person', '1-14cat', '1-15cat', '1-1bird', '1-1mouse', '1-1nmouses', '1-1person', '1-1cat', '1-2bird', '1-2mouse', '1-2nmouses', '1-2person', '1-2cat', '1-3bird', '1-3mouse', '1-3nmouses', '1-3person', '1-3cat', '2-14cat', '2-15cat', '2-16cat', '2-1bird', '2-1mouse', '2-1nmouses', '2-1person', '2-1cat', '2-2bird', '2-2mouse', '2-2nmouses', '2-2person']
def mysort(x,y):
x1=""
y1=""
for myletter in x :
if myletter.isdigit() or "-" in myletter:
x1=x1+myletter
x1 = x1.split("-")
for myletter in y :
if myletter.isdigit() or "-" in myletter:
y1=y1+myletter
y1 = y1.split("-")
if x1[0]>y1[0]:
return 1
elif x1[0]==y1[0]:
if x1[1]>y1[1]:
return 1
elif x1==y1:
return 0
else :
return -1
else :
return -1
myList.sort(mysort)
print myList
Thanks !
Martin
You have some good ideas with splitting on '-' and using isalpha() and isdigit(), but then we'll use those to create a function that takes in an item and returns a "clean" version of the item, which can be easily sorted. It will create a three-digit, zero-padded representation of the first number, then a similar thing with the second number, then the "word" portion (instead of just the first character). The result looks something like "001001bird" (that won't display - it'll just be used internally). The built-in function sorted() will use this callback function as a key, taking each element, passing it to the callback, and basing the sort order on the returned value. In the test, I use the * operator and the sep argument to print it without needing to construct a loop, but looping is perfectly fine as well.
def callback(item):
phrase = item.split('-')
first = phrase[0].rjust(3, '0')
second = ''.join(filter(str.isdigit, phrase[1])).rjust(3, '0')
word = ''.join(filter(str.isalpha, phrase[1]))
return first + second + word
Test:
>>> myList = ['1-10bird', '1-10mouse', '1-10nmouses', '1-10person', '1-10cat', '1-11bird', '1-11mouse', '1-11nmouses', '1-11person', '1-11cat', '1-12bird', '1-12mouse', '1-12nmouses', '1-12person', '1-13mouse', '1-13nmouses', '1-13person', '1-14bird', '1-14mouse', '1-14nmouses', '1-14person', '1-14cat', '1-15cat', '1-1bird', '1-1mouse', '1-1nmouses', '1-1person', '1-1cat', '1-2bird', '1-2mouse', '1-2nmouses', '1-2person', '1-2cat', '1-3bird', '1-3mouse', '1-3nmouses', '1-3person', '1-3cat', '2-14cat', '2-15cat', '2-16cat', '2-1bird', '2-1mouse', '2-1nmouses', '2-1person', '2-1cat', '2-2bird', '2-2mouse', '2-2nmouses', '2-2person']
>>> print(*sorted(myList, key=callback), sep='\n')
1-1bird
1-1cat
1-1mouse
1-1nmouses
1-1person
1-2bird
1-2cat
1-2mouse
1-2nmouses
1-2person
1-3bird
1-3cat
1-3mouse
1-3nmouses
1-3person
1-10bird
1-10cat
1-10mouse
1-10nmouses
1-10person
1-11bird
1-11cat
1-11mouse
1-11nmouses
1-11person
1-12bird
1-12mouse
1-12nmouses
1-12person
1-13mouse
1-13nmouses
1-13person
1-14bird
1-14cat
1-14mouse
1-14nmouses
1-14person
1-15cat
2-1bird
2-1cat
2-1mouse
2-1nmouses
2-1person
2-2bird
2-2mouse
2-2nmouses
2-2person
2-14cat
2-15cat
2-16cat
You need leading zeros. Strings are sorted alphabetically with the order different from the one for digits. It should be
'01-1bird'
'01-1mouse'
'01-1nmouses'
'01-2mouse'
'01-2nmouses'
'01-3bird'
'10-1birds'
As you you see 1 goes after 0.
The other answers here are very respectable, I'm sure, but for full credit you should ensure that your answer fits on a single line and uses as many list comprehensions as possible:
import itertools
[''.join(r) for r in sorted([[''.join(x) for _, x in
itertools.groupby(v, key=str.isdigit)]
for v in myList], key=lambda v: (int(v[0]), int(v[2]), v[3]))]
That should do nicely:
['1-1bird',
'1-1cat',
'1-1mouse',
'1-1nmouses',
'1-1person',
'1-2bird',
'1-2cat',
'1-2mouse',
...
'2-2person',
'2-14cat',
'2-15cat',
'2-16cat']
I am getting my feet wet with Python. I never done any programming or what so ever before and I really would appreciate it if someone would explain his_hers answer and not just post it since I want to learn something! Even better would be not posting the answere, but just giving hints what I should look at or something :)
I have several lists with a lot of values (numbers) one the one side.
On the other side, I have a URL which needs to be updated by the numbers out of the several lists and then be saved into another list for further process.
#borders of the bbox
longmax = 15.418483 #longitude top right
longmin = 4.953142 #longitude top left
latmax = 54.869808 #latitude top
latmin = 47.236219 #latitude bottom
#longitude
longstep = longmax - longmin
longstepx = longstep / 100 #longitudal steps the model shall perfom
#latitude
latstep = latmax - longmin
latstepx = latstep / 100 #latitudal steps the model shall perform
#create list of steps through coordinates longitude
llong = []
while longmin < longmax:
longmin+=longstepx
llong.append(+longmin)
#create list of steps through coordinates latitude
llat = []
while latmin < latmax:
latmin+=latstepx
llat.append(+latmin)
#create the URLs and store in list
for i in (llong):
"https://api.flickr.com/services/rest/?method=flickr.photos.search&format=json&api_key=5....lback=1&page=X&per_page=500&bbox=i&accuracy=1&has_geo=1&extras=geo,tags,views,description",sep="")"
As you can see, I try to make a request to the REST API from flickr.
What I dont understand is:
How do I get the loop to go through my lists, insert the values from the list to a certain point in the URL?
How to I tell the loop to save each URL separately after it inserted the first number out of list "llong" and "llat" and then proceed with the two next numbers.
Any hints?
You can use string formatting to insert whatever you want into your url:
my_list=["foo","bar","foobar"]
for word in my_list:
print ("www.google.com/{}".format(word))
www.google.com/foo
www.google.com/bar
www.google.com/foobar
The {} is used in your string wherever you want to insert.
To save them to a list you can use zip, insert using string formatting and then append to a new list.
urls=[]
for lat,lon in zip(llat,llong):
urls.append("www.google.com/{}{}".format(lat,lon))
Python string formatting: % vs. .format
I think the .format() method is the preferred method as opposed to using the "www.google.com/%s" % lat syntax.
There are answers here that discuss some of the differences.
The zip function is best explained with an example:
Say we have 2 lists l1 and l2:
l1 = [1,2,3]
l2 = [4,5,6]
If we use zip(l1,l2)the result will be:
[(1, 4), (2, 5), (3, 6)]
Then when we loop over the two zipped lists like below:
for ele_1,ele_2 in zip(l1,l2):
first iteration ele_1 = 1, ele_2 = 4
second iteration ele_1 = 2 ele_2 = 5 and so on ...
myUrls=[]
for i in range len(llat) # len(llong) is valid if both have same size.
myUrls.append(newUrl(llat[i]),llong[i])
def newUrl(lat,long):
return "www.flickr.......lat="+lat+".....long="+long+"...."
I wrote a script in Python removing tabs/blank spaces between two columns of strings (x,y coordinates) plus separating the columns by a comma and listing the maximum and minimum values of each column (2 values for each the x and y coordinates). E.g.:
100000.00 60000.00
200000.00 63000.00
300000.00 62000.00
400000.00 61000.00
500000.00 64000.00
became:
100000.00,60000.00
200000.00,63000.00
300000.00,62000.00
400000.00,61000.00
500000.00,64000.00
10000000 50000000 60000000 640000000
This is the code I used:
import string
input = open(r'C:\coordinates.txt', 'r')
output = open(r'C:\coordinates_new.txt', 'wb')
s = input.readline()
while s <> '':
s = input.readline()
liste = s.split()
x = liste[0]
y = liste[1]
output.write(str(x) + ',' + str(y))
output.write('\n')
s = input.readline()
input.close()
output.close()
I need to change the above code to also transform the coordinates from two decimal to one decimal values and each of the two new columns to be sorted in ascending order based on the values of the x coordinate (left column).
I started by writing the following but not only is it not sorting the values, it is placing the y coordinates on the left and the x on the right. In addition I don't know how to transform the decimals since the values are strings and the only function I know is using %f and that needs floats. Any suggestions to improve the code below?
import string
input = open(r'C:\coordinates.txt', 'r')
output = open(r'C:\coordinates_sorted.txt', 'wb')
s = input.readline()
while s <> '':
s = input.readline()
liste = string.split(s)
x = liste[0]
y = liste[1]
output.write(str(x) + ',' + str(y))
output.write('\n')
sorted(s, key=lambda x: x[o])
s = input.readline()
input.close()
output.close()
thanks!
First, try to format your code according to PEP8—it'll be easier to read. (I've done the cleanup in your post already).
Second, Tim is right in that you should try to learn how to write your code as (idiomatic) Python not just as if translated directly from its C equivalent.
As a starting point, I'll post your 2nd snippet here, refactored as idiomatic Python:
# there is no need to import the `string` module; `.strip()` is a built-in
# method of strings (i.e. objects of type `str`).
# read in the data as a list of pairs of raw (i.e. unparsed) coordinates in
# string form:
with open(r'C:\coordinates.txt') as in_file:
coords_raw = [line.strip().split() for line in in_file.readlines()]
# convert the raw list into a list of pairs (2-tuples) containing the parsed
# (i.e. float not string) data:
coord_pairs = [(float(x_raw), float(y_raw)) for x_raw, y_raw in coords_raw]
coord_pairs.sort() # you want to sort the entire data set, not just values on
# individual lines as in your original snippet
# build a list of all x and y values we have (this could be done in one line
# using some `zip()` hackery, but I'd like to keep it readable (for you at
# least)):
all_xs = [x for x, y in coord_pairs]
all_ys = [y for x, y in coord_pairs]
# compute min and max:
x_min, x_max = min(all_xs), max(all_xs)
y_min, y_max = min(all_ys), max(all_ys)
# NOTE: the above section performs well for small data sets; for large ones, you
# should combine the 4 lines in a single for loop so as to NOT have to read
# everything to memory and iterate over the data 6 times.
# write everything out
with open(r'C:\coordinates_sorted.txt', 'wb') as out_file:
# here, we're doing 3 things in one line:
# * iterate over all coordinate pairs and convert the pairs to the string
# form
# * join the string forms with a newline character
# * write the result of the join+iterate expression to the file
out_file.write('\n'.join('%f,%f' % (x, y) for x, y in coord_pairs))
out_file.write('\n\n')
out_file.write('%f %f %f %f' % (x_min, x_max, y_min, y_max))
with open(...) as <var_name> gives you guaranteed closing of the file handle as with try-finally; also, it's shorter than open(...) and .close() on separate lines. Also, with can be used for other purposes, but is commonly used for dealing with files. I suggest you look up how to use try-finally as well as with/context managers in Python, in addition to everything else you might have learned here.
Your code looks more like C than like Python; it is quite unidiomatic. I suggest you read the Python tutorial to find some inspiration. For example, iterating using a while loop is usually the wrong approach. The string module is deprecated for the most part, <> should be !=, you don't need to call str() on an object that's already a string...
Then, there are some errors. For example, sorted() returns a sorted version of the iterable you're passing - you need to assign that to something, or the result will be discarded. But you're calling it on a string, anyway, which won't give you the desired result. You also wrote x[o] where you clearly meant x[0].
You should be using something like this (assuming Python 2):
with open(r'C:\coordinates.txt') as infile:
values = []
for line in infile:
values.append(map(float, line.split()))
values.sort()
with open(r'C:\coordinates_sorted.txt', 'w') as outfile:
for value in values:
outfile.write("{:.1f},{:.1f}\n".format(*value))