从代码中学Python语法三（持续更新）

# -*- coding:utf-8 -*-
from collections import deque
__author__ = ‘hunterhug‘
mylist = [2, 3, 4, 5]
print(mylist)
mylist.append(3) # 添加元素到链尾
print(mylist)
mylist[mylist.__len__():]=[5]
print(mylist)
mylist.extend(mylist)  # 链表叠加
print(mylist)
mylist.insert(1, ‘d‘)  # 在位置前插入元素
print(mylist)
# mylist.remove(‘n‘) # 移除元素，没有该元素则出错
mylist.pop()  # 删除尾巴，并返回该元素
print(mylist)
mylist.pop(1)  # 删除指定位置元素
print(mylist)
print(mylist.index(3))  # 找出元素位置
print(mylist.count(3))  # 统计元素出现次数
print(mylist)
print(mylist.reverse())  # 倒排链表返回None
print(mylist)
mylist.sort(reverse=True)  # 排序降序
print(mylist)

# 链表作为堆栈，先进后出
stack1 = [2, 3, 4, 5]
stack1.append(1)
print(stack1)
stack1.pop()
print(stack1)

# 队列
queue=deque(stack1)
print(queue)
queue.append(1)  # 从后面插入
print(queue)
queue.appendleft(1)  # 从前面插入
print(queue)
queue.pop()
print(queue)  # 从后面删除
queue.popleft()
print(queue)  # 从前面删除

# 列表推导式
s = []
for i in range(10):
    s.append(i**2)
print(s)
s1 = [x**2 for x in range(10)]
print(s1)
s2 = [(x, y) for x in [1, 2, 3] for y in [3, 1, 4] if x != y]
print(s2)

freshfruit = [‘  banana‘, ‘  loganberry ‘, ‘passion fruit  ‘]
s3 = [weapon.strip() for weapon in freshfruit]
print(s3)
s4 = [(x, x**2) for x in range(6)]
print(s4)

vec = [[1,2,3], [4,5,6], [7,8,9]]
s5 = [num for elem in vec for num in elem]
print(s5)

from math import pi
s6 = [str(round(pi, i)) for i in range(100,102)]
print(s6)

# 矩阵转置
matrix = [
[1, 2, 3, 4],
[5, 6, 7, 8],
[9, 10, 11, 12],
]
s7 = [[row[i] for row in matrix] for i in range(4)]
print(s7)

# 等价于下面
transposed = []
for i in range(4):
    transposed.append([row[i] for row in matrix])
print(transposed)

print(list(zip(*matrix)))

# 删除利器
j = [3, 4]
del j[0]
print(j)
j.extend([3, 3])
print(j)
del j[0:2]
print(j)

# 元组，不可变
t = 12345, 54321, ‘hello!‘
print(t[0])
u = t, [33, 22]
print(u)

u[1].pop()
print(u)

# 序列拆封
a, b = u
print(a)
print(b)

empty = ()
print(len(empty))
print(empty.count(2)) # 找不到2这个元素

c = "dd",  # 单元素元组
print(c)

# 集合，无序不重复
basket = {‘apple‘, ‘orange‘, ‘apple‘, ‘pear‘, ‘orange‘, ‘banana‘}
# 字典
# 大括号或 set() 函数可以用来创建集合。
# 注意：想要创建空集合，你必须使用 set() 而不是 {} 。
# 后者用于创建空字典，
print(basket)
print(‘crabgrass‘ in basket)

a = set(‘abracadabra‘)
b = set(‘alacazam‘)
print(‘a:‘, a)
print(‘b:‘, b)
print(a - b)  # 在a中但不在b中元素
print(a | b)  # 在a或在b中元素
print(a & b)  # 在a且在b中元素
print(a ^ b)  # 或减去且

a = {x for x in ‘abracadabra‘ if x not in ‘abc‘}
print(a)

# 字典
tel = {‘jack‘: 4098, ‘sape‘: 4139}
print(list(tel.keys()))
print(sorted(tel.keys(),reverse=True))
print("h" in tel)

tel1 = dict([(‘sape‘, 4139), (‘guido‘, 4127), (‘jack‘, 4098)])
print(tel1)

tel2 = {x: x**2 for x in (2, 4, 6)}
print(tel2)

tel3 = dict(sape=4139, guido=4127, jack=4098)
print(tel3)

for k, v in tel3.items():
    print(k, ",", v)

# 序列中循环
for i, v in enumerate([‘tic‘, ‘tac‘, ‘toe‘]):
     print(i, v)

for i, v in enumerate((‘tic‘, ‘tac‘, ‘toe‘)):
     print(i, v)

for i, v in enumerate({‘tic‘:"j", ‘tac‘:"", ‘toe‘:"g"}):
     print(i, v)

# 整体打包
questions = [‘name‘, ‘quest‘, ‘favorite color‘]
answers = [‘lancelot‘, ‘the holy grail‘, ‘blue‘]
for q, a in zip(questions, answers):
    print(‘What is your {0}?  It is {1}.‘.format(q, a))
for i in reversed(range(1, 10, 2)):
    print(i)

asket = [‘apple‘, ‘orange‘, ‘apple‘, ‘pear‘, ‘orange‘, ‘banana‘]
for f in sorted(set(basket)):
    print(f)

print((1, 2, 3) < (1, 2, 4))

string1, string2, string3 = ‘‘, ‘Trondheim‘, ‘Hammer Dance‘
non_null = string1 or string2 or string3
print(non_null)

#http://docs.pythontab.com/python/python3.4/modules.html