Deep copy a list in Python -

i have problem list copy:

so after got e0 'get_edge', make copy of e0 calling 'e0_copy = list(e0)'. here guess e0_copy deep copy of e0, , pass e0_copy 'karger(e)'. in main function.
why result of 'print e0[1:10]' before loop not same after loop?

below code:

def get_graph():     f=open('kargermincut.txt')     g={}     line in f:         ints = [int(x) x in line.split()]         g[ints[0]]=ints[1:len(ints)]     return g  def get_edge(g):     e=[]     in range(1,201):         v in g[i]:             if v>i:                 e.append([i,v])     print id(e)     return e  def karger(e):     import random     count=200      while 1:         if count == 2:             break         edge = random.randint(0,len(e)-1)         v0=e[edge][0]         v1=e[edge][1]                            e.pop(edge)         if v0 != v1:             count -= 1             i=0             while 1:                 if == len(e):                     break                 if e[i][0] == v1:                     e[i][0] = v0                 if e[i][1] == v1:                     e[i][1] = v0                 if e[i][0] == e[i][1]:                     e.pop(i)                     i-=1                 i+=1      mincut=len(e)     return mincut   if __name__=="__main__":     import copy     g = get_graph()     results=[]     e0 = get_edge(g)     print e0[1:10]               ## result not equal print2     k in range(1,5):         e0_copy=list(e0)         ## guess here e0_coypy deep copy of e0         results.append(karger(e0_copy))        #print "the result %d" %min(results)     print e0[1:10]               ## print2 

thanks in advance!

e0_copy not deep copy. don't make deep copy using list() (both list(...) , testlist[:] shallow copies).

you use copy.deepcopy(...) deep copying list.

deepcopy(x, memo=none, _nil=[])     deep copy operation on arbitrary python objects. 

see following snippet -

>>> = [[1, 2, 3], [4, 5, 6]] >>> b = list(a) >>> [[1, 2, 3], [4, 5, 6]] >>> b [[1, 2, 3], [4, 5, 6]] >>> a[0][1] = 10 >>> [[1, 10, 3], [4, 5, 6]] >>> b   # b changes -> not deepcopy. [[1, 10, 3], [4, 5, 6]] 

now see deepcopy operation

>>> import copy >>> b = copy.deepcopy(a) >>> [[1, 10, 3], [4, 5, 6]] >>> b [[1, 10, 3], [4, 5, 6]] >>> a[0][1] = 9 >>> [[1, 9, 3], [4, 5, 6]] >>> b    # b doesn't change -> deep copy [[1, 10, 3], [4, 5, 6]]