df1 = pd.DataFrame({'lkey': ['foo', 'bar', 'baz', 'foo'],
                     'value1': [1, 2, 3, 5],
                     'value2': [5, 7, 8, 9]})
dfc = [['lkey','value1'],['lkey','value2']]


rslt = pd.DataFrame()
for i in range(0,1):
    tmp = df1[dfc[i]].rename(columns={ df1[dfc[i]].columns[0]: "test" })
    if len(rslt) == 0:
        rslt = tmp
    else:
        rslt = pd.merge(rslt, tmp,how='outer',on="test")

test    value1
0   foo 1
1   bar 2
2   baz 3
3   foo 5

test value1 value2
0   foo    1     6
1   bar    2     7
2   baz    3     8
3   foo    5     9

print (list(range(0,1)))
[0]

print (list(range(0,2)))
#alternative
#print (list(range(2)))
[0, 1]

rslt = pd.DataFrame()
for i in range(0,2):
    tmp = df1[dfc[i]].rename(columns={ df1[dfc[i]].columns[0]: "test" })
    if len(rslt) == 0:
        rslt = tmp
    else:
        rslt = pd.merge(rslt, tmp,how='outer',on="test")

print (rslt)
  test  value1  value2
0  foo       1       5
1  foo       1       9
2  foo       5       5
3  foo       5       9
4  bar       2       7
5  baz       3       8