流程控制--for序列

In [2]: list1 = [1,2,3,4]

In [3]: for i in list1:
   ...:     print i
   ...:
1
2
3
4

In [4]: for i in list1:
    print i,
   ...:
1 2 3 4

//range(头，尾，走多少步取值)
In [7]: range(0,10)
Out[7]: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

In [8]: range(0,10,1)
Out[8]: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

In [9]: range(0,10,2)
Out[9]: [0, 2, 4, 6, 8]

In [10]: range(0,10,3)
Out[10]: [0, 3, 6, 9]

In [11]: range(0,10,4)
Out[11]: [0, 4, 8]

 

[root@localhost test1]# vim 8.py
//ADD
#!/usr/bin/python

for i in [i**2 for i in range(1,11) if i % 2 != 0]:
    print i,

[root@localhost test1]# python 8.py
1 9 25 49 81

==================================
[root@localhost test1]# vim 9.py
//add
#!/usr/bin/python

sum = 0
for i in range(1,101):
    sum += i

print sum

[root@localhost test1]# python 9.py
5050

 

/* xrange() 可以生成迭代的对象 ，

    但是如果直接执行时， 不会显示任何。

    需要在for循环语句中使用，才能发挥作用。
*/
In [1]: for i in xrange(10):
   ...:     print i
   ...:
0
1
2
3
4
5
6
7
8
9

In [2]: for i in xrange(10):
    print i,
   ...:
0 1 2 3 4 5 6 7 8 9

In [3]: xrange(10)
Out[3]: xrange(10)

 

 

//两种方式新建字典
In [4]: dic = {'a':1, 'b':2}

In [5]: dic1 = dic.fromkeys('abc',10)

In [6]: dic
Out[6]: {'a': 1, 'b': 2}

In [7]: dic1
Out[7]: {'a': 10, 'b': 10, 'c': 10}

In [8]: for k in dic:
   ...:     print k
   ...:
a
b

//取keys
In [9]: for k in dic1:
    print k
   ...:
a
c
b

//并取values
In [11]: for k in dic1:
    print k, dic1[k]
   ....:
a 10
c 10
b 10

//格式化的输出
In [12]: for k in dic1:
    print "%s --> %s" % (k, dic1[k])
   ....:
a --> 10
c --> 10
b --> 10

 

 

//两种的区别
In [13]: for i in dic1.items():print i
('a', 10)
('c', 10)
('b', 10)

In [14]: for k, v in dic1.iteritems():print k, v
a 10
c 10
b 10

 

/* 利用循环做 “九九乘法表” */
[root@localhost test1]# vim 10.py
//ADD
#!/usr/bin/python

for i in xrange(1,10):
    for j in xrange(1, i+1):
        print "%sx%s=%s" % (j, i, j*i),
    print

/* 这里利用 逗号 来进行分行，并且打印出来 */

[root@localhost test1]# python 10.py
1x1=1
1x2=2 2x2=4
1x3=3 2x3=6 3x3=9
1x4=4 2x4=8 3x4=12 4x4=16
1x5=5 2x5=10 3x5=15 4x5=20 5x5=25
1x6=6 2x6=12 3x6=18 4x6=24 5x6=30 6x6=36
1x7=7 2x7=14 3x7=21 4x7=28 5x7=35 6x7=42 7x7=49
1x8=8 2x8=16 3x8=24 4x8=32 5x8=40 6x8=48 7x8=56
1x9=9 2x9=18 3x9=27 4x9=36 5x9=45 6x9=54 7x9=63