python中for循环的用法1+2+3…+50的和_python结束for循环

range(stop)                      #0 ~ stop-1
range(start,stop)                #start ~ stop-1
range(start,stop,step)           #start ~ stop-1， step表示步长

enumerate(X,[start=0])

a = { 
   1: 1, 2: 2, 3: 3}
for i , item in enumerate(a):
    print (i, item)
 
Output:
0 1
1 2
2 3

b = [1,2,3,4,5,6]
for i,item in enumerate(b, start=10):
    print(i,item)
 
Output:
10 1
11 2
12 3
13 4
14 5
15 6