python-運算符與表達式、控制流

運算符 的功能是完成某件事，它們由如+這樣的符號或者其他特定的關鍵字表示。運算符需要
數據來進行運算，這樣的數據被稱爲 操作數 。在這個例子中，2和3是操作數。

使用表達式：

#!/usr/bin/python
# Filename: expression.py
length = 5
breadth = 2
area = length * breadth
print 'Area is', area
print 'Perimeter is', 2 * (length + breadth)

結果：

Area is 10
Perimeter is 14

控制流：
在Python中有三種控制流語句——if、for和while

if 代碼

#!/usr/bin/python
# Filename: if.py
number = 23
guess = int(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

在raw_input() 在python 3中不能使用 而應該是使用 input()

while 語句

number = 23
running = True
while running:
guess = int(input('Enter an integer : '))
if guess == number:
print 'Congratulations, you guessed it.'
running = False # this causes the while loop to stop
elif guess < number:
print 'No, it is a little higher than that'
else:
print 'No, it is a little lower than that'
else:
print 'The while loop is over.'
# Do anything else you want to do here

for循環

for i in range(1, 5):
print i
else:
print 'The for loop is over'