Python 生成全排列

def print_res(a):
print(a)
def swap(a, i, j):
temp = a[i]
a[i] = a[j]
a[j] = temp
def dfs(a, depth):
if depth == len(a):
print_res(a)
for i in range(depth, len(a)):
swap(a, i, depth)
dfs(a, depth + 1)
swap(a, depth, i)
a = [1, 3, 5, 7]
dfs(a, 0)