I use networkx.add_edge(),but nothing of edges added? why?

Question

import networkx as net

def get_Children(g, df):
    for i in range(0, (df.iloc[:,0].size)-1):
        f1 = df.iloc[i]['firm1']
        f2 = df.iloc[i]['firm2']
        if f1 != f2:     
            if df.iloc[i]['children'] == 1.0:
                g.add_edge(f1, f2)
            else: continue
    return g
g = net.Graph()
g.add_nodes_from(index)
get_Children(g, df)

data like this:

firm1 firm2 children

• firm1 firm2 children
• 1 2 0
• 1 3 1
• 1 4 0
• 2 3 1
• 2 1 0
• 2 4 1
• 3 1 0
• 3 2 0
• 3 4 0
• 4 1 0
• 4 2 0
• 4 3 0

if firm1 is the children of firm2 then get 1 otherwise 0.

but i use the function above add nothing of edges.

In [177]: g.edges()

Out[177]: EdgeView([])

Answer 1

I have tried to reproduce your code here and I seem to have been able to produce edges with add_edge() using mostly the code you provided:

import pandas as pd
import networkx as nx 

df = pd.DataFrame({'firm1':[1,1,1,2,2,2,3,3,3,4,4,4], 
                   'firm2':[2,3,4,3,1,4,1,2,4,1,2,3], 
                   'children':[0,1,0,1,0,1,0,0,0,0,0,0]})

This gives the DataFrame you provided:

    children    firm1   firm2
0   0   1   2
1   1   1   3
2   0   1   4
3   1   2   3
4   0   2   1
5   1   2   4
6   0   3   1
7   0   3   2
8   0   3   4
9   0   4   1
10  0   4   2
11  0   4   3

I replicated the rest of your code, and the only thing I changed was replacing index with [1,2,3,4] (and also net with nx, the convention for the NetworkX package:

def get_Children(g, df):
    for i in range(0, (df.iloc[:,0].size)-1):
        f1 = df.iloc[i]['firm1']
        f2 = df.iloc[i]['firm2']
        if f1 != f2:     
            if df.iloc[i]['children'] == 1.0:
                g.add_edge(f1, f2)
            else: continue
    return g

g = nx.Graph()
g.add_nodes_from([1,2,3,4])
get_Children(g, df)
g.edges()

The g.edges() results in:

EdgeView([(1, 3), (2, 3), (2, 4)])

I'm using Python 3 to reproduce this. Perhaps you were using an incorrect value for index?