Python find position of element in array

Question

I have a CSV containing weather data like max and min temperatures  precipitation  longitude and latitude of the weather stations etc  Each category of data is stored in a single column    I want to find the location of the maximum and minimum temperatures  Finding the max or min is easy  numpy min my temperatures column   How can I find the position of where the min or max is located  so I can find the latitude and longitude   Here is my attempt    def coldest location data    coldest temp  numpy min mean temp       for i in mean temp           if mean temp i     -24 6              print i      Error  List indices must be int   I saved each of the columns of my CSV into variables  so they are all individual lists   lat             row 0  for row in weather data     latitude long            row 1  for row in weather data     longitude mean temp       row 2  for row in weather data     mean temperature    I have resolved the problem as per the suggestion list index x   mean temp index coldest temp    coldest location  long 5  lat 5      Unsure if asking a second question within a question is proper  but what if there are two locations with the same minimum temperature  How could I find both and their indices

User · Answer

Suppose if the list is a collection of objects like given below:

obj =  [
        {

            "subjectId" : "577a54c09c57916109142248", 
            "evaluableMaterialCount" : 0, 
            "subjectName" : "ASP.net"

        }, 
        {

            "subjectId" : "56645cd63c43a07b61c2c650", 
            "subjectName" : ".NET",         
        }, 
        {

            "subjectId" : "5656a2ec3c43a07b61c2bd83", 
            "subjectName" : "Python",

        }, 
        {

            "subjectId" : "5662add93c43a07b61c2c58c", 
            "subjectName" : "HTML"
        }
    ]

You can use the following method to find the index. Suppose the subjectId is 5662add93c43a07b61c2c58c then to get the index of the object in the list,

subjectId = "5662add93c43a07b61c2c58c"

for i, subjobj in enumerate(obj):
    if(subjectId == subjobj['subjectId']):
        print(i)

User · Answer

In the NumPy array  you can use where like this  np where npArray    20

User · Answer

For your first question  find the position of some value in a list x using index    like so   x index value    For your second question  to check for multiple same values you should split your list into chunks and use the same logic from above  They say divide and conquer  It works  Try this   value   1  x    1 2 3 4 5 6 2 1 4 5 6   chunk a   x  int len x  2     get the first half of x  chunk b   x int len x  2      get the rest half of x  print chunk a index value   print chunk b index value     Hope that helps

User · Answer

There is a built in method for doing this   numpy where     You can find out more about it in the excellent detailed documentation

User · Answer

Without actually seeing your data it is difficult to say how to find location of max and min in your particular case  but in general  you can search for the locations as follows  This is just a simple example below   In  9   a np array  5 1 2 3 10 4    In  10   np where a    a min    Out 10    array  1      In  11   np where a    a max    Out 11    array  4       Alternatively  you can also do as follows   In  19   a np array  5 1 2 3 10 4    In  20   a argmin   Out 20   1  In  21   a argmax   Out 21   4

User · Answer

You should do   try      value index   my list index value  except      value index   -1

User · Answer

As Aaron states  you can use  index value   but because that will throw an exception if value is not present  you should handle that case  even if you re sure it will never happen  A couple options are by checking its presence first  such as   if value in my list      value index   my list index value    or by catching the exception as in   try      value index   my list index value  except      value index   -1   You can never go wrong with proper error handling

User · Answer

I would assume your variable mean temp already has the values loaded in to it and is nX1 dimension  i e only one row   Now to achieve what you want  you can    Change the datatype of your variable   def coldest location data        mean temp   numpy mat mean temp   data is now matrix type     min index   numpy nonzero mean temp    mean temp min       this returns list of indexes     print mean temp min index 0  min index 1     printing minimum value  i e -24 6 in you data i believe

User · Answer

Have you thought about using Python list s  index value  method  It return the index in the list of where the first instance of the value passed in is found

[python] Python: find position of element in array

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