working with arrays

[Safy]

Hello, i really need some help, im new to python so having a bit of trouble.
i have two arrays which i successfully pulled out from some data. i want to search these arrays for 2 number and when they appear i want their index.

>>> arrF = [3,4,5,6,7,8,9]
>>> arrid=[0,0,0,1,0,0,0]
>>> def indexOfObjectinFrame2(frame,arrF,arrID,id):
...  for i in arrF:
...    if arrF[i] == frame:
...      if arrid [i] == id:
...        print i
...      else:
...        print -1

no matter how many different ways i try this, it just wont work, i keep getting errors. why does python not like this?

[ghostdog74]

Hello, i really need some help, im new to python so having a bit of trouble.
i have two arrays which i successfully pulled out from some data. i want to search these arrays for 2 number and when they appear i want their index.

>>> arrF = [3,4,5,6,7,8,9]
>>> arrid=[0,0,0,1,0,0,0]
>>> def indexOfObjectin Frame2(frame,ar rF,arrID,id):
... for i in arrF:
... if arrF[i] == frame:
... if arrid [i] == id:
... print i
... else:
... print -1
no matter how many different ways i try this, it just wont work, i keep getting errors. why does python not like this?

its easy to "search" for array elements. use the "in" keyword (if you don't want to know the position.
eg

....
if frame in arrF and id in arrid:
   ....

another way,

...
for i in range(len(arrF)):
   if frame == arrF[i] and id == arrid[i]:
      .....

[bartonc]

Hello, i really need some help, im new to python so having a bit of trouble.
i have two arrays which i successfully pulled out from some data. i want to search these arrays for 2 number and when they appear i want their index.

>>> arrF = [3,4,5,6,7,8,9]
>>> arrid=[0,0,0,1,0,0,0]
>>> def indexOfObjectinFrame2(frame,arrF,arrID,id):
...  for i in arrF:
...    if arrF[i] == frame:
...      if arrid [i] == id:
...        print i
...      else:
...        print -1

no matter how many different ways i try this, it just wont work, i keep getting errors. why does python not like this?

While my friend ghostdog74 does show a better way (there are several) to get the index of an object in a LIST (arrays are a slightly different animal), I found your problem:

def indexOfObjectinFrame2(frame,arrF,arrID,id):
##    for i in arrF: This is 3,4,5,6,7,8,9
    for i in range(len(arrF)):
        if arrF[i] == frame:
            if arrid[i] == id:
                print i
            else:
                print -1

arrF = [3,4,5,6,7,8,9]
arrid=[0,0,0,1,0,0,0]

indexOfObjectinFrame2(6, arrF, arrid, 1)

I have used code tags and run this in a module so that you may copy and paste it into you module. If you do this, you won't have to retype the whole thing to make changes. Welcome to TheScripts.

[bartonc]

While my friend ghostdog74 does show a better way (there are several) to get the index of an object in a LIST (arrays are a slightly different animal), I found your problem:

def indexOfObjectinFrame2(frame,arrF,arrID,id):
##    for i in arrF: This is 3,4,5,6,7,8,9
    for i in range(len(arrF)):
        if arrF[i] == frame:
            if arrid[i] == id:
                print i
            else:
                print -1

arrF = [3,4,5,6,7,8,9]
arrid=[0,0,0,1,0,0,0]

indexOfObjectinFrame2(6, arrF, arrid, 1)

I have used code tags and run this in a module so that you may copy and paste it into you module. If you do this, you won't have to retype the whole thing to make changes. Welcome to TheScripts.

Or:

def indexOfObjectinFrame2(frame,arrF,arrID,id):
    for i, item in enumerate(arrF):     # This is [0,1,2...], [3,4,5...]
        if item == frame:
            if arrid[i] == id:
                print i
            else:
                print -1

arrF = [3,4,5,6,7,8,9]
arrid=[0,0,0,1,0,0,0]

indexOfObjectinFrame2(6, arrF, arrid, 1)

[Safy]

Wow thanks...i didnt think anyone would actually reply..This forum is great...thankks again guys..
Safy

[Safy]

okaay that worked fine, when i call this with another function it returns 'None'.
The data i am using is actually really large so i would like to call pass it numbers automatically, the code below looks fine to me ..why does is it not working?
just to refresh:
I have a series of arrays, I want to find the index of object '0' in frame F from the data.
When i have the index for the object, if that object exists in that
frame, i will analyse the data (some maths).(hope it makes sense)

arrayX = [190,193,197,198,201,201,201,202]
arrayY = [125,125,124,126,125,126,127,126]
arrF = [289,290,291,292,293,294,295,296]
arrid = [0,0,0,0,1,0,0,0]

def indexOfObjectinFrame(frame,arrF,arrID,id):
    for i in range(len(arrF)):
        if arrF[i] == frame:
            if arrid[i] == id:
                print i
            else:
                print -1000

def compareObjects(GTX,GTY,GTF,GTid,gtobjid):
  totalDistance = 0
  i = 0 
  while i <= 9: 
    print i                               #largest frame number in either file
    GTindex = indexOfObjectinFrame(i,GTF,GTid,gtobjid) 
    print "GTINDEX IS ", GTindex
   
    if GTindex >= 0: 
     print "index found"#, Total_distance here
    i = i+1 


# call above
C = compareObjects(arrX,arrY,arrF,arrid,0)  #...GT number here...,.tracker number here...)

Why does this say 'None' when executed?
Thanks,S

[bvdet]

okaay that worked fine, when i call this with another function it returns 'None'.
The data i am using is actually really large so i would like to call pass it numbers automatically, the code below looks fine to me ..why does is it not working?
just to refresh:
I have a series of arrays, I want to find the index of object '0' in frame F from the data.
When i have the index for the object, if that object exists in that
frame, i will analyse the data (some maths).(hope it makes sense)

arrayX = [190,193,197,198,201,201,201,202]
arrayY = [125,125,124,126,125,126,127,126]
arrF = [289,290,291,292,293,294,295,296]
arrid = [0,0,0,0,1,0,0,0]

def indexOfObjectinFrame(frame,arrF,arrID,id):
    for i in range(len(arrF)):
        if arrF[i] == frame:
            if arrid[i] == id:
                print i
            else:
                print -1000

def compareObjects(GTX,GTY,GTF,GTid,gtobjid):
  totalDistance = 0
  i = 0 
  while i <= 9: 
    print i                               #largest frame number in either file
    GTindex = indexOfObjectinFrame(i,GTF,GTid,gtobjid) 
    print "GTINDEX IS ", GTindex
   
    if GTindex >= 0: 
     print "index found"#, Total_distance here
    i = i+1 


# call above
C = compareObjects(arrX,arrY,arrF,arrid,0)  #...GT number here...,.tracker number here...)

Why does this say 'None' when executed?
Thanks,S

Use the 'return' statement to return a value. 'print' always returns 'None'. Here is a simple example:

def is_prime(n):
    count = 2
    while count < n**0.5:
        if n % count == 0:
            print '%d is a product of %d and %d' % (n, count, n/count)
            return False
        count += 1
    print n, 'is a prime number'
    return True

Notice there are two 'return' statements. If a condition is met, one value is returned. If not, further processing takes place and returns a different value.

[Safy]

Ahah..i got it..well i think this is right anyway.
in the code i included print statements everywhere hoping it will help me debug the code BUT as i already have print statements int he functions it was causing problems, so after removing them and sorting out 'global name errors' i have some index numbers :)

yaaay im not a programmer but i will get there :)
S

[bartonc]

Wow thanks...i didnt think anyone would actually reply..This forum is great...thankks again guys..
Safy

Glad you like it. Stick around. You'll learn tons.