从2d列表中获取x，y并继续

Question

I'm trying to take a 2d list of locations that incl lat/ longs and get only the coordinates from the list (in column 3 and 4) to send to another function so that distances can be calculated... but I'm totally stumped. What I have is...

EDITED from OP to show where I'm at... x1 = -18.00 #These values don't change y1 = 118.00
x2 = float(origList[3]) y2 = float(origList[4]) n = len(origList) appList = []

for i in range (n-1):
    appList.append(findDistance(x1, y1, x2, y2))
    print appList

But now I get...File "F:\\Storage\\t_2\\coord_find.py", line 27, in main,x2=math.fabs(origList[3]) TypeError: a float is required

So the problem is in the conversion to float???

Then all I have so far for the findDistance function (I only just started it and just want to test if arguments are being passed correctly)... def findDistance(x1, y1, x2, y2): cosX = math.fabs(y1 - y2) a = 90 - x2 b = 90 - x1

---

Here's my updated code that is giving me this...

delx = math.fabs(y1 - y2)

TypeError: unsupported operand type(s) for -: 'float' and 'list'

I'm posting it up because I obviously didn't give a clear enough explanation and have made some changes since. AS you can see, I want to get the x2,y2 from cols 3,4. Tried x2=float(origList[3]), y2=float(origList[4]) but that doesn't work either- I get "float()argument must be a string or a number". Do I need to split the list somehow before trying to extract the values as floats??

import csv
import math

def fZone():
    origList = [['200','12_7','Cons_pl','-20.10','120.10','C_10_T2'],['....'...]]
    # origList has 30+ lines like this
    x1 = -20.68     # Fixed point
    x2 = 117.19     # Fixed point
    n = len(origList)   # list length
    appList = []    # to hold returned 

    for i in range (n):
        x2= origList[3] # I wanna get the '-20.10' col each iteration
        y2= origList[4] # I wanna get the '120.10' col each iteration
        appList.append(findDist(x1, y1, x2, y2))
        print appList

def findDist(x1,y1,x2,y2):
    delx = math.fabs(y1 - y2)
        a = 90 - x2
        b = 90 - x1  # formula is not finished

Answer 1

Your origList[0:] evaluates to origList . Try origList[0] .

range(0,n-1) only goes up to n-2, and you have no need to specify the starting value of 0 since that's the default anyway. Use range(n) .

You say the coordinates are in columns 3 and 4. It looks like you're somewhat new to indexing in a programming language, so I hope I don't offend with a gratuitous reminder that you might be looking for list elements 2 and 3, if you mean that these are the 3rd and 4th columns.

Also, the print should be outside the loop.

Answer 2

Apparently your list is containing pairs of strings, not of numbers.

In Python this conversion is never automatic so you will probably have to change the code to:

findDistance(x1, y1, float(origList[i][3]), float(origList[i][4]))

An error like

lat2= float(stnList[3])
TypeError: float() argument must be a string or a number

clearly says what was passed to float was neither a number nor a string.

Just add a print repr(stnList[3]) right before the offending statement and check out what was passed instead.

You can also the python debugger to find what the problem is, check for example this short video of a pdb session example