python 学习

今天学习if语句和其他语言也没有其他区别，唯一需要提出的是用到 raw_input 函数，在调用该函数的过程中要注意函数的类型，例如int等

eg.

#!/usr/bin/python
# Filename: if.py

number = 23
guess = int(raw_input('Enter an integer : '))

if guess == number:
    print 'Congratulations, you guessed it.' # New block starts here
    print "(but you do not win any prizes!)" # New block ends here
elif guess < number:
    print 'No, it is a little higher than that' # Another block
    # You can do whatever you want in a block ...
else:
    print 'No, it is a little lower than that'
    # you must have guess > number to reach here

print 'Done'

运行结果：

[root@www jerry]# python if.py
Enter an integer : a
Traceback (most recent call last):
  File "for.py", line 5, in ?
    guess = int(raw_input('Enter an integer : '))
ValueError: invalid literal for int(): a
[root@www jerry]# python if.py
Enter an integer : 12
No, it is a little higher than that
Done
[root@www jerry]# python if.py
Enter an integer : 23
Congratulations, you guessed it.
(but you do not win any prizes!)
Done
[root@www jerry]# python if.py
Enter an integer : 24
No, it is a little lower than that
Done
[root@www jerry]#

但是如果去掉类型int呢？

guess = int(raw_input('Enter an integer : ')) 改成guess = raw_input('Enter an integer : ')

运行结果：

[root@www jerry]# python if.py
Enter an integer : a
No, it is a little lower than that
Done
[root@www jerry]#

PS：在Python中没有switch语句。你可以使用if..elif..else语句来完成同样的工作