骆秀韬 epsilon_luoo@outlook.com
聪明办法学 Python 教学团队
print( ) 与 注释¶
第一行代码
In [40]:
print("hello, world") # f(x)
hello, world
单行注释 使用 # 开头，# 后面的内容不会被当做代码，只能写在一行中
In [41]:
print("Datawhale") # for the learner，和学习者一起成长
Datawhale
In [42]:
# learn python the smart way v2
print("p2s")
# print("prepare to be smart")
p2s
每一个 print() 会默认换行
In [43]:
print("Data")
print("whale")
Data whale
In [44]:
print("Data", end="")
print("whale")
Datawhale
多个内容是以空格分隔
In [45]:
print("Data", "whale") # f(x, y)
Data whale
In [46]:
print("Data", "whale", sep="*")
Data*whale
列表与字典¶
列表是一种序列，它是可变的
容器的唯一作用就是打包、解包、内容传递。
In [47]:
p2s = ["learn", "python", "the", "smart", "way"] # f(x, y)
print(p2s)
['learn', 'python', 'the', 'smart', 'way']
In [48]:
print(p2s[1], p2s[0], p2s[-1], p2s[-2])
python learn way smart
In [49]:
print(p2s[0:2]) # 切片 左闭右开区间
print(p2s[2:]) # 起始：0，结束：-1
['learn', 'python'] ['the', 'smart', 'way']
字典是键值对的集合
In [50]:
dw_set = set() # 集合
for i in "Datawhale":
dw_set.add(i)
print(dw_set)
{'a', 'D', 'w', 'l', 'h', 'e', 't'}
In [51]:
dw_dict = {"d":"Data", "w":"whale"} # key:value
print(dw_dict["d"], dw_dict["w"], sep="")
Datawhale
字典的更新
In [52]:
dw_dict["w"] = "Whale"
print(dw_dict)
{'d': 'Data', 'w': 'Whale'}
女朋友说，下班回来带一个西瓜。如果看到番茄，就买两个
In [53]:
def 买西瓜(num):
return f"{num}个西瓜"
def 买番茄(num):
return f"{num}个番茄"
看到番茄 = True
In [54]:
# 下班了
西瓜 = 买西瓜(1)
if 看到番茄:
西瓜 = 买西瓜(2)
print(f"带了{西瓜}回家")
带了2个西瓜回家
In [55]:
# 女朋友心想
西瓜 = 买西瓜(1)
if 看到番茄:
番茄 = 买番茄(2)
print(f"带了{西瓜}和{番茄}回家")
带了1个西瓜和2个番茄回家
In [56]:
for row in range(3):
for col in range(3):
print("🐳", end="")
print()
🐳🐳🐳 🐳🐳🐳 🐳🐳🐳
In [57]:
for string in "learn python the smart way".split():
print(string)
learn python the smart way
In [58]:
print("我，秦始皇，V50，吃肯德基".split("，"))
['我', '秦始皇', 'V50', '吃肯德基']
自定义函数 与 return¶
A function is a procedure (a sequence of statements) stored under a name that can be used repeatedly by calling the name.
以 Rectified Linear Unit (ReLU) 函数为例，其数学表达式为：
$f(x) = \begin{cases} x, x > 0, \\ 0, x \leqslant 0. \end{cases}$
In [59]:
def ReLU(x): # f(x)
if x > 0:
return x
return 0
print(ReLU(9))
9
In [60]:
relu = lambda x: max(x, 0)
print(relu(-9))
0
一种基于深度抄袭的机器学习时间特征提取技术¶
直接赋值
In [61]:
a = [1, 2, 3, [4, 5]]
b = a
id(a) == id(b), id(a)
Out[61]:
(True, 2442188747328)
浅度抄袭
In [62]:
c = a.copy() # a:v1.0
a.append(6) # a:2.0
print(f"b: {b}\nc: {c}")
b: [1, 2, 3, [4, 5], 6] c: [1, 2, 3, [4, 5]]
In [63]:
print(f"a[3] => {a[3]}\n")
a[3].append(7) # a:3.0
print(f"b: {b}\nc: {c}")
a[3] => [4, 5] b: [1, 2, 3, [4, 5, 7], 6] c: [1, 2, 3, [4, 5, 7]]
深度抄袭
In [64]:
import copy
d = copy.deepcopy(a)
In [65]:
a[3].append(8)
print(f"b: {b}\nc: {c}\nd: {d}")
b: [1, 2, 3, [4, 5, 7, 8], 6] c: [1, 2, 3, [4, 5, 7, 8]] d: [1, 2, 3, [4, 5, 7], 6]
托马斯小火车与它的对象们¶
In [66]:
from random import choice
import time
from tqdm import tqdm
from IPython.display import display, HTML
class Train:
def __init__(self, name, *goods, naughty=True):
self.name = name
self.goods = goods
self.naughty = naughty
def __getitem__(self, idx):
return self.goods[idx]
def __len__(self):
return len(self.goods)
def info(self):
if self.name == "托马斯小火车":
return f"Hi，我是{self.name}，Cinders and ashes!"
return f"Hi，我是{self.name}"
def 发车(self, string):
print(f"{string}，上山！") # f-strings
for _ in tqdm(range(30)):
time.sleep(0.1)
display(HTML("<video controls width=1200 src='train.mp4'>train</video>"))
In [67]:
Edward = Train("爱德华", 1, 2.5, 9, 114, 514, naughty=False) # 实例化
In [68]:
Edward.info()
Out[68]:
'Hi，我是爱德华'
In [69]:
len(Edward)
Out[69]:
5
In [70]:
a, b= Edward[3], Edward[4] # 解包与打包 (114, 514) => a, b
print(f"hello {b}") # f-strings
hello 514
In [71]:
货物 = ["邮件", "大米", "煤矿", "劳斯莱斯"]
托马斯 = Train("托马斯小火车", *货物, naughty=True)
托马斯.info()
Out[71]:
'Hi，我是托马斯小火车，Cinders and ashes!'
In [72]:
len(托马斯)
Out[72]:
4
In [73]:
托马斯[2]
Out[73]:
'煤矿'
In [74]:
托马斯.发车("AE86")
AE86，上山！
100%|██████████| 30/30 [00:03<00:00, 9.08it/s]
