How can I get rid of this stack overflow problem in python for Kosaraju's algorithm?

Question

I'm a new programmer, and I'm working through Stanford's algorithms course on edX.

One of the programming assignments is to find strongly connected components using Kosaraju's algorithm, on a graph with ~1,000,000 vertices. My implementation is the most basic translation from the textbook's pseudo code into Python, and it works fine on smaller graphs, so I think it's correct.

With Python's default recursion limit of 1000 it reaches the limit.

I've tried sys.setrecursionlimit(1000000), but that doesn't help, and instead I get "Process finished with exit code -1073741571" which is a stack overflow.

I found these two pages for increasing stack size limits, but am not sure how to use either of them: Set stack size, ulimit command.

Another relevant bit of information is that Python doesn't optimize tail recursion, but I'm not sure that applies to my code as it currently is.

G = {}
for i in range(1, 875715):
    G[i] = [0]
for l in open('SCC.txt'):
    items = list(map(int, l.split()))
    G[items[0]].append(items[1])

Grev = {}
for i in range(1, 875715):
    Grev[i] = [0]
for l in open('SCC.txt'):
    items = list(map(int, l.split()))
    Grev[items[1]].append(items[0])

def TopoSort(G):
    for v in G:
        if G[v][0] == 0:
            DFStopo(G, v)

def DFStopo(G, s):
    G[s][0] = 1
    global orderedVertexList
    for v in G[s][1:]:
        if G[v][0] == 0:
            DFStopo(G, v)
    orderedVertexList.insert(0, s)

def Kosaraju(G, Grev):
    TopoSort(Grev)
    global numSCC
    for v in orderedVertexList:
        if G[v][0] == 0:
            numSCC = numSCC + 1
            DFSSCC(G, v)

def DFSSCC(G, s):
    G[s][0] = 1
    global SCC
    SCC.append(numSCC)
    for v in G[s][1:]:
        if G[v][0] == 0:
            DFSSCC(G, v)

numSCC = 0
orderedVertexList = []
SCC = []

Kosaraju(copy.deepcopy(G), copy.deepcopy(Grev))