bool
t, f = True, False
print type(t) # Prints "<type 'bool'>"
字符串
hello = 'hello' # 实在想不出的时候就用hello world
world = "world"
print hello, len(hello) # 字符串长度
列表，注意，python的容器可以容纳不同的数据类型，[ ] 中括号是列表
xs = [3, 1, 2] # 建一个列表
print xs, xs[2]
print xs[-1] # 用-1表示最后一个元素，输出来
[3, 1, 2] 2
2
xs.append('happy') # 可以用append在尾部添加元素
print xs
[3, 1, 'Hanxiaoyang', 'happy']
x = xs.pop() # 也可以把最后一个元素“弹射”出来
print x, xs
happy [3, 1, 'Hanxiaoyang']
列表切片
nums = range(5) # 0-4
print nums # 输出 "[0, 1, 2, 3, 4]"
print nums[2:4] # 下标2到4(不包括)的元素，注意下标从0开始
print nums[2:] # 下标2到结尾的元素; prints "[2, 3, 4]"
print nums[:2] # 直到下标2的元素; prints "[0, 1]"
print nums[:] # Get a slice of the whole list; prints ["0, 1, 2, 3, 4]"
print nums[:-1] # 直到倒数第一个元素; prints ["0, 1, 2, 3]"
nums[2:4] = [8, 9] # 也可以直接这么赋值
print nums # Prints "[0, 1, 8, 8, 4]"
[0, 1, 2, 3, 4]
[2, 3]
[2, 3, 4]
[0, 1]
[0, 1, 2, 3, 4]
[0, 1, 2, 3]
[2, 3]
[2, 3, 4]
[0, 1]
[0, 1, 2, 3, 4]
[0, 1, 2, 3]
[0, 1, 8, 9, 4]
animals = ['喵星人', '汪星人', '火星人']
for animal in animals:
print animal
喵星人
汪星人
汪星人
火星人
又要输出元素，又要输出下标怎么办，用
enumerate 函数:animals = ['喵星人', '汪星人', '火星人']
for idx, animal in enumerate(animals):
print '#%d: %s' % (idx + 1, animal)
#1: 喵星人
#2: 汪星人
#2: 汪星人
#3: 火星人
List comprehensions:
如果对list里面的元素都做一样的操作，然后生成一个list，用它最快了，这绝对会成为你最爱的python操作之一:
# 求一个list里面的元素的平方，然后输出，很out的for循环写法
nums = [0, 1, 2, 3, 4]
squares = []
for x in nums:
squares.append(x ** 2)
print squares
[0, 1, 4, 9, 16]
nums = [0, 1, 2, 3, 4]
# 对每个x完成一个操作以后返回来，组成新的list
squares = [x ** 2 for x in nums]
print squares
[0, 1, 4, 9, 16]
nums = [0, 1, 2, 3, 4]
# 把所有的偶数取出来，平方后返回
even_squares = [x ** 2 for x in nums if x % 2 == 0]
print even_squares
字典 { }是字典
d = {'cat': 'cute', 'dog': 'furry'} # 建立字典
print d['cat'] # 根据key取value
print 'cat' in d # 查一个元素是否在字典中
cute
True
d['fish'] = 'wet' # 设定键值对
print d['fish'] # 这时候肯定是输出修改后的内容
wet
print d['monkey'] # 不是d的键，肯定输不出东西
---------------------------------------------------------------------------
KeyError Traceback (most recent call last)
<ipython-input-6-f37735e1a686> in <module>()
----> 1 print d['monkey'] # 不是d的键，肯定输不出东西
KeyError Traceback (most recent call last)
<ipython-input-6-f37735e1a686> in <module>()
----> 1 print d['monkey'] # 不是d的键，肯定输不出东西
KeyError: 'monkey'
print d.get('monkey', 'N/A') # 可以默认输出'N/A'（取不到key对应的value值的时候）
print d.get('fish', 'N/A')
N/A
N/A
del d['fish'] # 删除字典中的键值对
print d.get('fish', 'N/A') # 这会儿就没有了
N/A
你可以这样循环python字典取出你想要的内容:
d = {'person': 2, 'cat': 4, 'spider': 8}
for animal in d:
legs = d[animal]
print 'A %s has %d legs' % (animal, legs)
A person has 2 legs
A spider has 8 legs
A spider has 8 legs
A cat has 4 legs
用iteritems函数可以同时取出键值对:
d = {'person': 2, 'cat': 4, 'spider': 8}
for animal, legs in d.iteritems():
print 'A %s has %d legs' % (animal, legs)
A person has 2 legs
A spider has 8 legs
A spider has 8 legs
A cat has 4 legs
nums = [0, 1, 2, 3, 4]
even_num_to_square = {x: x ** 2 for x in nums if x % 2 == 0}
print even_num_to_square
even_list = [ x ** 2 for x in nums if x % 2 == 0]
print even_list
{0: 0, 2: 4, 4: 16}
[0, 4, 16]
Set：不包含相同的元素，没有value，只有key，用{}表示
元组（tuple）：元组可以作为字典的key或者set的元素出现，但是list不可以作为字典的key或者set的元素。
d = {(x, x + 1): x for x in range(10)} # Create a dictionary with tuple keys
t = (5, 6) # Create a tuple
print type(t)
print d[t]
print d[(1, 2)]
<type 'tuple'>
5
1
5
1
函数
def sign(x):
if x > 0:
return 'positive'
elif x < 0:
return 'negative'
else:
return 'zero'
for x in [-1, 0, 1]:
print sign(x)
negative
zero
zero
positive
函数名字后面接的括号里，可以有多个参数，你自己可以试试:
def hello(name, loud=False):
if loud:
print 'HELLO, %s' % name.upper()
else:
print 'Hello, %s!' % name
hello('Bob')
hello('Fred', loud=True)
Hello, Bob!
HELLO, FRED
HELLO, FRED
类
class Greeter:
# 构造函数
def __init__(self, name):
self.name = name # Create an instance variable
# 类的成员函数
def greet(self, loud=False):
if loud:
print 'HELLO, %s!' % self.name.upper()
else:
print 'Hello, %s' % self.name
def hello(name, loud=False):
if loud:
print 'HELLO, %s' % name.upper()
else:
print 'Hello, %s!' % name
g = Greeter('Fred') # 构造一个类
g.greet() # 调用函数; prints "Hello, Fred"
g.greet(loud=True) # 调用函数; prints "HELLO, FRED!"
g.greet(True)
Hello, Fred
HELLO, FRED!
HELLO, FRED!
HELLO, FRED!
HELLO, FRED!