'''
Created on Feb 19, 2015

@author: Susan
'''
# Remove all negative numbers from a list                                                                     
''' 
def removeNegatives(numberlist):                                                                 
    answer = [] 
    for num in numberlist: 
        if num >= 0: 
            answer.append(num) 
    return answer 
 
print "removeNegatives" 
somenums = [3, -1, 8, -5, -2, 6, 7] 
print "somenums", somenums
nonegs = removeNegatives(somenums) 
print "somenums", somenums 
print "removed negs", nonegs 
somenums = [-1,-2,3]
print "somenums", somenums
nonegs = removeNegatives(somenums)                                                                                   
print "somenums", somenums
print "removed negs", nonegs
somenums = [3,2,-1]
print "somenums", somenums
nonegs = removeNegatives(somenums)                                                                                   
print "somenums", somenums 
print "remove negs", nonegs

'''
'''                                                                                
def removeNegatives2(numberlist):  
    y = range(len(numberlist)) 
    print "index list is", y                                                                                       
    for x in y:
        value = numberlist[x]
        if value < 0:
            numberlist.pop(x)
 
print "removeNegatives2"
somenums = [3, -1, 8, -5, -2, 6, 7]
print somenums
removeNegatives2(somenums)                                                                                   
print somenums 
somenums = [-1,-2,3]
print somenums
removeNegatives2(somenums)                                                                                   
print somenums 
somenums = [3,2,-1]
print somenums
removeNegatives2(somenums)                                                                                   
print somenums 


'''  
                                                                             
def removeNegatives3(numberlist):                                                                                        
    pos = 0; 
    while (True):
        if pos >= len(numberlist):
            break
        value = numberlist[pos]
        if value < 0: 
            numberlist.pop(pos) 
            pos = pos -1
        pos = pos + 1 

def removeNegatives3a(numberlist):                                                                                        
    pos = 0; 
    while (True):
        if pos >= len(numberlist):
            break
        value = numberlist[pos]
        if value < 0: 
            numberlist.pop(pos) 
        else:
            pos = pos + 1  
            
            
print "removeNegatives3"
somenums = [3, -1, 8, -5, -2, 6, 7]
print somenums 
removeNegatives3(somenums) 
print somenums 
somenums = [-1,-2,3]
print somenums
removeNegatives3(somenums)                                                                                   
print somenums 
somenums = [3,2,-1]
print somenums
removeNegatives3(somenums)                                                                                   
print somenums