Deep Learning Chapter02：Python基础语法回顾

# 注释内容

"""
	第一行注释
	第二行注释
	第三行注释
"""

'''
	注释1
	注释2
	注释3
'''

变量名 = 值

False     None    True   and      as       assert   break     class  
continue  def     del    elif     else     except   finally   for
from      global  if     import   in       is       lambda    nonlocal  not       or      pass   raise    return   try      while     with   yield

my_name = '北山啦'
print(my_name)

北山啦

input("提示信息")

address = input('请输入您的CSDN博客地址：')

请输入您的CSDN博客地址：https://beishan.blog.csdn.net/

print(f'您输入的密码是{address}')
# <class 'str'>
print(type(address))

您输入的密码是https://beishan.blog.csdn.net/
<class 'str'>

print('hello Python')

age = 18
print(age)

# 需求：输出“今年我的年龄是18岁”

age = 20
name = '北山啦'
student_id = '01830115'

print('我的名字是%s' % name, end='\n')
print('我的学号是%s' % student_id)
print(f'我的名字是{name},今年{age+1}岁了')

我的名字是北山啦
我的学号是01830115
我的名字是北山啦,今年21岁了

weight = 74.22
print(f"{weight}")
print("{:.3f}".format(weight))

74.22
74.220

stu_id = 1
print("{:03d}".format(stu_id))

001

num1 = 1
num2 = 1.1
print(type(num1))
print(type(num2))
print(type('北山啦'))
print(type(True))

<class 'int'>
<class 'float'>
<class 'str'>
<class 'bool'>

num = input('请输入您的幸运数字：')
print(f"您的幸运数字是{num}")
print(type(num))
print(type(int(num)))

# 1. float() -- 转换成浮点型
num1 = 1
print(float(num1))
print(type(float(num1)))

# 2. str() -- 转换成字符串类型
num2 = 10
print(type(str(num2)))

# 3. tuple() -- 将一个序列转换成元组
list1 = [10, 20, 30]
print(tuple(list1))
print(type(tuple(list1)))


# 4. list() -- 将一个序列转换成列表
t1 = (100, 200, 300)
print(list(t1))
print(type(list(t1)))

# 5. eval() -- 将字符串中的数据转换成Python表达式原本类型
str1 = '10'
str2 = '[1, 2, 3]'
str3 = '(1000, 2000, 3000)'
print(type(eval(str1)))
print(type(eval(str2)))
print(type(eval(str3)))

请输入您的幸运数字：20
您的幸运数字是20
<class 'str'>
<class 'int'>
1.0
<class 'float'>
<class 'str'>
(10, 20, 30)
<class 'tuple'>
[100, 200, 300]
<class 'list'>
<class 'int'>
<class 'list'>
<class 'tuple'>

if 条件:
    条件成立执行的代码

if 条件:
    条件成立执行的代码
else:
    条件不成立执行的代码

if 条件1:
    条件1成立执行的代码
elif 条件2:
    条件2成立执行的代码
else:
    以上条件都不成立执行的代码

age = int(input('请输入他的年龄：\n'))
if age < 18:
    print(f"你输入的年龄是{age},童工")
elif 18 <= age <= 60:
    print("你输入的年龄是{},合法".format(age))
elif age > 60:
    print("你输入的年龄是%d,退休" % age)

请输入他的年龄：
20
你输入的年龄是20,合法

"""
提示：0-石头，1-剪刀，2-布
1. 出拳
玩家输入出拳
电脑随机出拳,使用random库随机生成0，1，2
"""
import random
computer = random.randint(0, 2)
# print(computer)
player = int(input('请出拳：0-石头，1-剪刀，2-布：'))

if (player == 0 and computer == 1) or (player == 1 and computer == 2) or (player == 2 and computer == 0):
    print('玩家获胜')
elif player == computer:
    print('平局')
else:
    print('电脑获胜')

请出拳：0-石头，1-剪刀，2-布：2
电脑获胜

条件成立执行代码

# 输出5遍博客名
t = 0
while(t < 5):
    print("北山啦")
    t += 1

北山啦
北山啦
北山啦
北山啦
北山啦

# 1-100累加
i = 1
sum = 0
while i <= 100:
    sum += i
    i += 1
print(sum)

5050

i = 1
sum = 0
while i <= 100:
    if i % 2 == 0:
        sum += i
    i += 1
print(sum)

2550

i = 0
sum = 0
while i <= 100:
    sum += i
    i += 2
print(sum)

2550

# 循环吃5个苹果，吃完了第3个吃饱了，第4和第5个不吃了
i = 1
while i <= 5:
    if i == 4:
        break
    print(f"吃了第{i}个苹果")
    i += 1

吃了第1个苹果
吃了第2个苹果
吃了第3个苹果

i = 1
while i <= 5:
    if i == 3:
        print("吃出了一个大虫子，这个苹果不吃了")
        # 如果使用continue，在continue之前一定要修改计数器，否则进入死循环
        i += 1
        continue
    print(f"吃了第{i}个苹果")
    i += 1

吃了第1个苹果
吃了第2个苹果
吃出了一个大虫子，这个苹果不吃了
吃了第4个苹果
吃了第5个苹果

j = 0
while j < 3:
    i = 0
    while i < 3:
        print("CSDN")
        i += 1
    j += 1
    print("北山啦")

CSDN
CSDN
CSDN
北山啦
CSDN
CSDN
CSDN
北山啦
CSDN
CSDN
CSDN
北山啦

j = 0
while j < 5:
    i = 0
    while i < 5:
        print("*", end='')
        i += 1
    print()
    j += 1

*****
*****
*****
*****
*****

j = 0
while j < 5:
    i = 0
    while i <= j:
        print("*", end='')
        i += 1
    print()
    j += 1

*
**
***
****
*****

# 九九乘法表
for i in range(1, 10):
    for j in range(1, i+1):
        print(f'{j}*{i}={i*j}\t', end='')
    print()

1x1=1	
1x2=2	2x2=4	
1x3=3	2x3=6	3x3=9	
1x4=4	2x4=8	3x4=12	4x4=16	
1x5=5	2x5=10	3x5=15	4x5=20	5x5=25	
1x6=6	2x6=12	3x6=18	4x6=24	5x6=30	6x6=36	
1x7=7	2x7=14	3x7=21	4x7=28	5x7=35	6x7=42	7x7=49	
1x8=8	2x8=16	3x8=24	4x8=32	5x8=40	6x8=48	7x8=56	8x8=64	
1x9=9	2x9=18	3x9=27	4x9=36	5x9=45	6x9=54	7x9=63	8x9=72	9x9=81	

# 九九乘法表
i = 1
while i <= 9:
    j = 1
    while(j <= i):
        print('{}*{}= {}'.format(j, i, i*j), end='\t')
        j += 1
    print('')
    i += 1

1*1= 1	
1*2= 2	2*2= 4	
1*3= 3	2*3= 6	3*3= 9	
1*4= 4	2*4= 8	3*4= 12	4*4= 16	
1*5= 5	2*5= 10	3*5= 15	4*5= 20	5*5= 25	
1*6= 6	2*6= 12	3*6= 18	4*6= 24	5*6= 30	6*6= 36	
1*7= 7	2*7= 14	3*7= 21	4*7= 28	5*7= 35	6*7= 42	7*7= 49	
1*8= 8	2*8= 16	3*8= 24	4*8= 32	5*8= 40	6*8= 48	7*8= 56	8*8= 64	
1*9= 9	2*9= 18	3*9= 27	4*9= 36	5*9= 45	6*9= 54	7*9= 63	8*9= 72	9*9= 81	

print('\n'.join(
    ['\t'.join([f"{j}*{i}={i*j}" for j in range(1, i + 1)]) for i in range(1, 10)]))

1*1=1
1*2=2	2*2=4
1*3=3	2*3=6	3*3=9
1*4=4	2*4=8	3*4=12	4*4=16
1*5=5	2*5=10	3*5=15	4*5=20	5*5=25
1*6=6	2*6=12	3*6=18	4*6=24	5*6=30	6*6=36
1*7=7	2*7=14	3*7=21	4*7=28	5*7=35	6*7=42	7*7=49
1*8=8	2*8=16	3*8=24	4*8=32	5*8=40	6*8=48	7*8=56	8*8=64
1*9=9	2*9=18	3*9=27	4*9=36	5*9=45	6*9=54	7*9=63	8*9=72	9*9=81

重复执行的代码1

重复执行的代码2

......

str1 = 'CSDN北山啦'
for i in str1:
    print(i)

C
S
D
N
北
山
啦

# break
str2 = 'https://beishan.blog.csdn.net/'
for i in str2:
    if i == ':':
        break
    print(i)
else:
    print("循环正常结束执行的else代码")

h
t
t
p
s

# continue
str2 = 'https://beishan.blog.csdn.net/'
for i in str2:
    if i == ':':
        continue
    print(i)
else:
    print("循环正常结束执行的else代码")

h
t
t
p
s
/
/
b
e
i
s
h
a
n
.
b
l
o
g
.
c
s
d
n
.
n
e
t
/
循环正常结束执行的else代码

a = 'https://beishan.blog.csdn.net/'
print(type(a))
b = """原创:CSDN北山啦"""
print(type(b))
c = "I'm 北山啦"
print(c)
print(type(c))

<class 'str'>
<class 'str'>
I'm 北山啦
<class 'str'>

序列[开始位置下标:结束位置下标:步长]

1. 不包含结束位置下标对应的数据， 正负整数均可；
2. 步长是选取间隔，正负整数均可，默认步长为1。

name = "abcdefg"

print(name[2:5:1])  # cde
print(name[2:5])  # cde
print(name[:5])  # abcde
print(name[1:])  # bcdefg
print(name[:])  # abcdefg
print(name[::2])  # aceg
print(name[:-1])  # abcdef, 负1表示倒数第一个数据
print(name[-4:-1])  # def
print(name[::-1])  # gfedcba

cde
cde
abcde
bcdefg
abcdefg
aceg
abcdef
def
gfedcba

字符串序列.split(分割字符, num)

字符或子串.join(多字符串组成的序列)

name_list = ['欢迎', '关注', '北山啦']
print(name_list[0])
print(name_list[1])
print(name_list[2])

欢迎
关注
北山啦

name_list = ['欢迎', '关注', '北山啦']
print(name_list.index('北山啦'))
print(name_list.count('北山啦'))c
print(len(name_list))

2
1
3

name_list = ['欢迎', '关注', '北山啦']
print('欢迎' in name_list)
print('Lilys' in name_list)

True
False

print('北山' not in name_list)
print('Lilys' not in name_list)

True
True

import random
teachers = ['zhangzk', 'dfbdaf', 'dfad', 'dfa', 'etw', 'dfa', 'dgdag']
offices = [[], [], []]
for name in teachers:
    num = random.randint(0, 2)
    offices[num].append(name)
print(offices)

[['dfbdaf', 'dfa'], ['zhangzk', 'dfa', 'dgdag'], ['dfad', 'etw']]

[i for j in offices for i in j]

['dfbdaf', 'dfa', 'zhangzk', 'dfa', 'dgdag', 'dfad', 'etw']

for name in offices:
    for i in name:
        print(i, end=' ')

etw dgdag dfad dfa zhangzk dfbdaf dfa 

t1 = (10, 20, 30)
t2 = (10,)
print(type(t1))
print(type(t2))

<class 'tuple'>
<class 'tuple'>

t2 = (10,)
print(type(t2))  # tuple

t3 = (20)
print(type(t3))  # int

t4 = ('hello')
print(type(t4))  # str

<class 'tuple'>
<class 'int'>
<class 'str'>

dict1 = {'name': 'Tom', 'age': 20, 'gender': '男'}  # 有数据的字典
dict2 = {}  # 创建空字典
dict3 = dict()  # 创建空字典
print(type(dict1))

<class 'dict'>

dict1 = {'name': '北山啦', 'age': 20, 'gender': '男'}
dict1['name'] = 'Rose'
print(dict1)

{'name': 'Rose', 'age': 20, 'gender': '男'}

dict1['id'] = 110
print(dict1)

{'name': 'Rose', 'age': 20, 'gender': '男', 'id': 110}

dict1 = {'name': '北山啦', 'age': 20, 'gender': '男'}
# del(dict1)
del dict1['gender']
print(dict1)

{'name': '北山啦', 'age': 20}

dict1.clear()
print(dict1)  # 清空字典

{}

dict1 = {'name': '北山啦', 'age': 20, 'gender': '男'}
dict1['age'] = 22
print(dict1)

{'name': '北山啦', 'age': 22, 'gender': '男'}

dict1 = {'name': '北山啦', 'age': 20, 'gender': '男'}
print(dict1['name'])
print(dict1['id'])

北山啦



---------------------------------------------------------------------------

KeyError                                  Traceback (most recent call last)

C:\Users\ADMINI~1\AppData\Local\Temp/ipykernel_1196/2064109912.py in <module>
      1 dict1 = {'name':'北山啦','age':20,'gender':'男'}
      2 print(dict1['name'])
----> 3 print(dict1['id'])


KeyError: 'id'

字典序列.get(key, 默认值)

dict1 = {'name': 'Tom', 'age': 20, 'gender': '男'}
print(dict1.get('name'))  # Tom
print(dict1.get('id', 110))  # 110
print(dict1.get('id'))  # None

dict1 = {'name': 'Tom', 'age': 20, 'gender': '男'}
print(dict1.keys())  # dict_keys(['name', 'age', 'gender'])

dict1 = {'name': 'Tom', 'age': 20, 'gender': '男'}
print(dict1.values())  # dict_values(['Tom', 20, '男'])

dict1 = {'name': 'Tom', 'age': 20, 'gender': '男'}
print(dict1.items())  # dict_items([('name', 'Tom'), ('age', 20), ('gender', '男')])

dict1 = {'name': '北山啦', 'age': 20, 'gender': '男'}
for key in dict1.keys():
    print(key)

name
age
gender

for value in dict1.values():
    print(value)

北山啦
20
男

dict1 = {'name': 'Tom', 'age': 20, 'gender': '男'}
for item in dict1.items():
    print(item)

('name', 'Tom')
('age', 20)
('gender', '男')

dict1 = {'name': 'Tom', 'age': 20, 'gender': '男'}
for key, value in dict1.items():
    print(f'{key}:{value}')

name:Tom
age:20
gender:男

s1 = {10, 20, 30, 40, 50}
print(s1)

s2 = {10, 30, 20, 10, 30, 40, 30, 50}
print(s2)

s3 = set('abcdefg')
print(s3)

s4 = set()
print(type(s4))  # set

s5 = {}
print(type(s5))  # dict

{50, 20, 40, 10, 30}
{50, 20, 40, 10, 30}
{'a', 'd', 'b', 'e', 'f', 'g', 'c'}
<class 'set'>
<class 'dict'>

s1 = {10, 20, 30, 40, 50}
s1.add(100)  # 集合是可变的类型
print(s1)

{50, 20, 100, 40, 10, 30}

s1.update([30, 40, 50, 60, 70])
s1  # 集合可以去掉重复数据

{10, 20, 30, 40, 50, 60, 70}

s1.remove(10)

s1

{20, 30, 40, 50, 60, 70}

s1.discard(10)  # 没有该数据不会报错，remove会报错
s1

{20, 30, 40, 50, 60, 70}

enumerate(可遍历对象, start=0)

list1 = ['a', 'b', 'c', 'd', 'e']
for i in enumerate(list1, 1):
    print(i)

(1, 'a')
(2, 'b')
(3, 'c')
(4, 'd')
(5, 'e')

for index, char in enumerate(list1, start=1):
    print(f'下标是{index}, 对应的字符是{char}')

下标是1, 对应的字符是a
下标是2, 对应的字符是b
下标是3, 对应的字符是c
下标是4, 对应的字符是d
下标是5, 对应的字符是e

# while实现
list1 = []
i = 0
while i < 10:
    list1.append(i)
    i += 1
print(list1)

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

# for循环实现
list1 = []
for i in range(10):
    list1.append(i)
print(list1)

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

list1 = [i for i in range(10)]
print(list1)

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

# 创建0-10的偶数列表
list1 = [i for i in range(0, 11, 2)]
print(list1)

[0, 2, 4, 6, 8, 10]

list1 = [i for i in range(0, 11) if i % 2 == 0]
print(list1)

[0, 2, 4, 6, 8, 10]

list1 = []
for i in range(1, 3):
    for j in range(3):
        list1.append((i, j))
print(list1)

[(1, 0), (1, 1), (1, 2), (2, 0), (2, 1), (2, 2)]

list1 = [(i, j) for i in range(1, 3) for j in range(3)]
print(list1)

[(1, 0), (1, 1), (1, 2), (2, 0), (2, 1), (2, 2)]

a = [[1, 2, 3], [1, 2, 3], [1, 2, 3]]
b = [x for b in a for x in b]
print(b)

[1, 2, 3, 1, 2, 3, 1, 2, 3]

dict1 = {i: i**2 for i in range(1, 5)}
print(dict1)

{1: 1, 2: 4, 3: 9, 4: 16}

list1 = ['name', 'age', 'gender']
list2 = ['beishan', 20, 'man']

dict1 = {list1[i]: list2[i] for i in range(len(list1))}
print(dict1)

{'name': 'beishan', 'age': 20, 'gender': 'man'}

counts = {'MBP': 268, 'HP': 125, 'DELL': 201, 'Lenovo': 199, 'acer': 99}
count1 = {key: value for key, value in counts.items() if value >= 200}
print(count1)

{'MBP': 268, 'DELL': 201}

list1 = [1, 1, 2]
set1 = {i**2 for i in list1}
print(set1)

{1, 4}

def 函数名():
    代码1
    代码2
    ...

函数名()

return 表达式

def 函数名():
    """ 函数说明文档 """

def 函数名(参数):
    代码1
    代码2
    ......

函数名(参数)

1. 不同的需求，参数可有可无。
2. 在Python中，函数必须==先定义后使用==。

def sum_num(a, b):
    return a + b


# 用result变量保存函数返回值
result = sum_num(1, 2)
print(result)

3

def 函数名(参数):
    """ 说明文档的位置 """
    代码
    ......

help(函数名)

help(print)

Help on built-in function print in module builtins:

print(...)
    print(value, ..., sep=' ', end='\n', file=sys.stdout, flush=False)
    
    Prints the values to a stream, or to sys.stdout by default.
    Optional keyword arguments:
    file:  a file-like object (stream); defaults to the current sys.stdout.
    sep:   string inserted between values, default a space.
    end:   string appended after the last value, default a newline.
    flush: whether to forcibly flush the stream.

def sum_num(a, b):
    """ 求和函数 """
    return a + b


help(sum_num)

Help on function sum_num in module __main__:

sum_num(a, b)
    求和函数

def testB():
    print('---- testB start----')
    print('这里是testB函数执行的代码...(省略)...')
    print('---- testB end----')


def testA():
    print('---- testA start----')
    testB()
    print('---- testA end----')


testA()

---- testA start----
---- testB start----
这里是testB函数执行的代码...(省略)...
---- testB end----
---- testA end----

def testA():
    a = 100

    print(a)


testA()  # 100
print(a)  # 报错：name 'a' is not defined

a = 100 # 定义全局变量a


def testA():
    print(a)  # 访问全局变量a，并打印变量a存储的数据


def testB():
    print(a)  # 访问全局变量a，并打印变量a存储的数据


testA()  # 100
testB()  # 100

 UnboundLocalError: local variable 'count' referenced before assignment

a = 100  # 定义全局变量a


def testA():
    print(a)


def testB():
    global a
    a = 200
    print(a)


testA()
testB()

100
200

def return_num():
    return 1
    return 2


result = return_num()
print(result)  # 1

def return_num():
    return 1, 2


result = return_num()
print(result)  # (1, 2)

def return_num():
    return (10, 20)


return_num()

(10, 20)

def user_info(name, age, gender):
    print(f'您的名字是{name}, 年龄是{age}, 性别是{gender}')


user_info('北山啦', 20, '男')

您的名字是北山啦, 年龄是20, 性别是男

def user_info(name, age, gender):
    print(f'您的名字是{name}, 年龄是{age}, 性别是{gender}')


user_info('Rose', age=20, gender='女')
user_info('小明', gender='男', age=16)

您的名字是Rose, 年龄是20, 性别是女
您的名字是小明, 年龄是16, 性别是男

user_info(gender='男', age=16, '小明')

  File "C:\Users\ADMINI~1\AppData\Local\Temp/ipykernel_13808/292338224.py", line 1
    user_info(gender='男', age=16,'小明')
                                     ^
SyntaxError: positional argument follows keyword argument

def user_info(name, age, gender='男'):
    print(f'您的名字是{name}, 年龄是{age}, 性别是{gender}')


user_info('TOM', 20)
user_info('Rose', 18, '女')

您的名字是TOM, 年龄是20, 性别是男
您的名字是Rose, 年龄是18, 性别是女

def user_info(*args):#*必须写，args可以为其他的
    print(args)


# ('TOM',)
user_info('TOM')
# ('TOM', 18)
user_info('TOM', 18)

def user_info(**kwargs):
    print(kwargs)


# {'name': 'TOM', 'age': 18, 'id': 110}
user_info(name='TOM', age=18, id=110)

def return_num():
    return 100, 200


num1, num2 = return_num()
print(num1)
print(num2)

100
200

dict1 = {'name': 'beishanla', 'age': 20}
a, b = dict1
print(a)
print(b)

name
age

for i in dict1.keys():
    print(i)

name
age

lambda 参数列表 ： 表达式

def sum_number(num):
   if num == 1:
       return 1
   return num + sum_number(num-1)
sum_number(3)

f1 = lambda x,y:x+y
print(f1(1, 2))

3

f2 = lambda a,b:a if a > b else b
f2(1000,5000)

5000

infos = [
    {'name': 'beishanla', 'age': 20},
    {'name': 'zhagnzk', 'age': 21},
    {'name': 'zhangy', 'age': 22},
]

infos.sort(key=lambda x: x['name'], reverse=True)
print(infos)

[{'name': 'zhangy', 'age': 22}, {'name': 'zhagnzk', 'age': 21}, {'name': 'beishanla', 'age': 20}]

square = list(map(lambda x: x**2, range(10)))
print(square)

[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

square = [x**2 for x in range(10)]
print(square)

[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

result = list(filter(lambda x: x % 2 == 0, range(10)))
result

[0, 2, 4, 6, 8]

import functools

list1 = [1, 2, 3, 4, 5]


def func(a, b):
    return a + b


result = functools.reduce(func, list1)

print(result)  # 15

15

文件对象 = open(目标文件, 访问模式)
  
 with open(目标文件,访问模式):

文件对象.read()
文件对象.readlines()
文件对象.readline()

文件对象.write()

文件对象.close()