Inserting values from list to string python

Question

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:

1. How do I get the loop to go through my lists, insert the values from the list to a certain point in the URL?
2. 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?

Answer 1

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 ...

Answer 2

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+"...."