【Python】-008-语句表达式-条件/循环

1.条件语句

语法

if xxx: statements1
elif: statements2
else: statements3

其他用法

逻辑表达式：not / and / or / 1<x<3

2.循环语句

while举例

#判断输入的整数是否为质数
y = input('Pleae a number:')
x = y//2
flag = 1

while x > 1:
  if y%x == 0:
    flag = 0
    print y,'has factor, ', x
    # break
  x = x - 1;

if flag == 1:
  print y,'is prime number.'
else:
  print y,'is not a prime number.' 

for举例

#遍历字符串/元组
s = u'你在远方'
t = (u'我', u'在', u'故乡')
for i in s: print '\b'+i,
for j in t: print '\b'+j,
#遍历字典，并写入文件
d = {'name': 'Bob', 'age': 33, 'gender': 'male'}
file = open('test.txt', 'w')
for key in d:
    print >> file, key, '==>', d[key]
file.close()
# 读取文件内容，体会while和for两种方式差别
file = open('test.txt', 'r')
while True:
  line = file.readline()
  if not line: break
  print line.strip()
file.close()

for line in open('test.txt', 'r'):
  print line.strip()