python if语句使用范例代码

if语句用来检验一个条件， 如果 条件为真，我们运行一块语句（称为 if-块 ）， 否则 我们处理另外一块语句（称为 else-块 ）。 else 从句是可选的。

#!/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'
# This last statement is always executed, after the if statement is executed

输出结果

$&nbsppython&nbspif.py
Enter&nbspan&nbspinteger&nbsp:&nbsp50
No,&nbspit&nbspis&nbspa&nbsplittle&nbsplower&nbspthan&nbspthat
Done
$&nbsppython&nbspif.py
Enter&nbspan&nbspinteger&nbsp:&nbsp22
No,&nbspit&nbspis&nbspa&nbsplittle&nbsphigher&nbspthan&nbspthat
Done
$&nbsppython&nbspif.py
Enter&nbspan&nbspinteger&nbsp:&nbsp23
Congratulations,&nbspyou&nbspguessed&nbspit.
(but&nbspyou&nbspdo&nbspnot&nbspwin&nbspany&nbspprizes!)
Done