Python-基础语法

一、注释

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# this is Single-Line Comments

"""
this is block comments,By Double quotation marks

Author: lol_toulan
Date: 2024-12-16 23:59:59
"""

'''
this is block comments,By Single quotation marks

Author: lol_toulan
Date: 2024-12-16 23:59:59
'''

二、语法格式

在Java和C等语言中，我们常以 {}对来表示代码块，以;来标志一行或多行代码的结束

但是在Python中，我们常以缩进来区分不同的代码块，通常也不需要;来标志一行或多行代码的结束

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def print_hi(name):
    # Use a breakpoint in the code line below to debug your script.
    print(f'Hi, {name}')  # Press Ctrl+F8 to toggle the breakpoint.


# Press the green button in the gutter to run the script.
if __name__ == '__main__':
    print_hi('PyCharm')
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public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("hello world");
    }
}

三、数据类型

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a = 123
b = 1.23
c = "123"
d = '123'
e = 4+5j
f = True
g = None
h = b'123'
# 不可变
i = (a, b,c,d,e,f,g,h)
# 可变
j = [a,b,c,d,e,f,g,h]
k = {'name':'lol','age':18}
l = {'name','lol','age',18}
# 不可变
o = frozenset({'name','lol','age',18})

m = """
this is multiline comment 
"""

n = '''
this is multiline comment 
'''

def method_name(name):
    for element in name:
        print(f"{element} \t ==> type is  {type(element)}")

array = [a,b,c,d,e,f,g,h,i,j,k,l,o,m,n]
method_name(array)

image-20241217212420173

四、IF判断

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a = 123
b = 1.23
c = "123"
d = '123'
e = 4 + 5j
f = True
g = None
h = b'123'
# 不可变
i = (a, b, c, d, e, f, g, h)
# 可变
j = [a, b, c, d, e, f, g, h]
k = {'name': 'lol', 'age': 18}
l = {'name', 'lol', 'age', 18}
# 不可变
o = frozenset({'name', 'lol', 'age', 18})


def if_method(names):
    for name in names:
        if type(name) == int:
            print(f"{name} \t ==> is int")
        elif type(name) == float:
            print(f"{name} \t ==> is float")
        elif type(name) == str:
            print(f"{name} \t ==> is str")
        elif type(name) == complex:
            print(f"{name} \t ==> is complex")
        elif type(name) == bool:
            print(f"{name} \t ==> is bool")
        elif type(name) == type(None):
            print(f"{name} \t ==> is None")
        elif type(name) == bytes:
            print(f"{name} \t ==> is bytes")
        elif type(name) == tuple:
            print(f"{name} \t ==> is tuple")
        elif type(name) == list:
            print(f"{name} \t ==> is list")
        elif type(name) == dict:
            print(f"{name} \t ==> is dict")
        elif type(name) == set:
            print(f"{name} \t ==> is set")
        else:
            print(f"{name} \t ==> is {type(name).__name__}")


array = [a, b, c, d, e, f, g, h, i, j, k, l, o]
if_method(array)

a = 10
b = 20

if (a and b):
    print("1 - 变量 a 和 b 都为 true")
else:
    print("1 - 变量 a 和 b 有一个不为 true")

if (a or b):
    print("2 - 变量 a 和 b 都为 true，或其中一个变量为 true")
else:
    print("2 - 变量 a 和 b 都不为 true")

# 修改变量 a 的值
a = 0
if (a and b):
    print("3 - 变量 a 和 b 都为 true")
else:
    print("3 - 变量 a 和 b 有一个不为 true")

if (a or b):
    print("4 - 变量 a 和 b 都为 true，或其中一个变量为 true")
else:
    print("4 - 变量 a 和 b 都不为 true")

if not (a and b):
    print("5 - 变量 a 和 b 都为 false，或其中一个变量为 false")
else:
    print("5 - 变量 a 和 b 都为 true")

a = 10
b = 20
list = [1, 2, 3, 4, 5]

if (a in list):
    print("1 - 变量 a 在给定的列表中 list 中")
else:
    print("1 - 变量 a 不在给定的列表中 list 中")

if (b not in list):
    print("2 - 变量 b 不在给定的列表中 list 中")
else:
    print("2 - 变量 b 在给定的列表中 list 中")

# 修改变量 a 的值
a = 2
if (a in list):
    print("3 - 变量 a 在给定的列表中 list 中")
else:
    print("3 - 变量 a 不在给定的列表中 list 中")

a = 20
b = 20

if (a is b):
    print("1 - a 和 b 有相同的标识")
else:
    print("1 - a 和 b 没有相同的标识")

if (id(a) == id(b)):
    print("2 - a 和 b 有相同的标识")
else:
    print("2 - a 和 b 没有相同的标识")

# 修改变量 b 的值
b = 30
if (a is b):
    print("3 - a 和 b 有相同的标识")
else:
    print("3 - a 和 b 没有相同的标识")

if (a is not b):
    print("4 - a 和 b 没有相同的标识")
else:
    print("4 - a 和 b 有相同的标识")

a = [1, 2, 3, 4]
b = a
print(id(a))
print(id(b))
if (a is b) and (a == b) and (id(a) == id(b)):
    print("1 - a 和 b 有相同的标识，并且 a 等于 b")
else:
    print("1 - a 和 b 没有相同的标识，或者 a 等于 b")

a = [1, 2, 3, 4]
b = a[:]
print(id(a))
print(id(b))
if (a is b) and (a == b):
    print("1 - a 和 b 有相同的标识，并且 a 等于 b")
else:
    print("1 - a 和 b 没有相同的标识，或者 a 等于 b")

if (id(a) == id(b)):
    print("2 - a 和 b 有相同的标识")
else:
    print("2 - a 和 b 没有相同的标识")

image-20241217214313728

五、SWITCH…CASE…

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def http_error(status):
    match status:
        case 400:
            return "Bad request"
        case 404:
            return "Not found"
        case 418:
            return "I'm a teapot"
        case _:
            return "Something's wrong with the internet"

mystatus=400
print(f" {mystatus} ==> {http_error(mystatus)}")

mystatus=500
print(f" {mystatus} ==> {http_error(mystatus)}")

image-20241217215031208

六、FOR循环

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sites = ["Baidu", "Google", "Runoob", "Taobao"]
for site in sites:
    print(site)
print()

word = 'runoob'
for letter in word:
    print(letter)

print()
#  1 到 5 的所有数字：
for number in range(1, 6):
    print(f"range(1, 6) ==> {number}")


print()
for number in range(1, 6, 2):
    print(f"range(1, 6, 2) ==> {number}")



print()
for number in range(0, 6, 2):
    print(f"range(0, 6, 2) ==> {number}")


print()
sites = ["Baidu", "Google", "Runoob", "Taobao"]
for site in range(len(sites)):
    print(f"循环数据 {site} ==> {sites[site]}")


print()
runoob = "Runoob"
for x in range(len(runoob)):
    print(f"range('Runoob') {x} ==> {runoob[x]}")


print()
for x in range(6):
    print(f"range(6) ==> {x}")
else:
    print("Finally finished!")


print()
sites = ["Baidu", "Google", "Runoob", "Taobao"]
for site in sites:
    if site == "Runoob":
        print("菜鸟教程!")
        break
    print("循环数据 " + site)
else:
    print("没有循环数据!")
print("完成循环!")

image-20241217221017121

七、WHILE循环

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n = 100

sum = 0
counter = 1
while counter <= n:
    sum = sum + counter
    counter += 1
    if(counter % 10 == 0):
        print(f"{sum} ==> {counter}")
print("1 到 %d 之和为: %d" % (n, sum))

image-20241217221304861

八、类型转换

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print("-------------------------------------------------------------------------------------")
print("隐式类型转换")
# int + int = int
# int + float = float
# float + float = float

num_int = 123
num_flo = 1.23

num_new = num_int + num_flo

print("num_int 数据类型为:", type(num_int))
print("num_flo 数据类型为:", type(num_flo))

print("num_new 值为:", num_new)
print("num_new 数据类型为:", type(num_new))

# int + str = 报错
# float + str = 报错
# str + str = str
# char + str = str


num_int = 123
num_str = "456"

print("num_int 数据类型为:", type(num_int))
print("num_str 数据类型为:", type(num_str))

# TypeError: unsupported operand type(s) for +: 'int' and 'str'
# print(num_int+num_str)

# TypeError: unsupported operand type(s) for +: 'float' and 'str'
# print(num_flo+num_str)

# TypeError: ord() expected a character, but string of length 3 found
# print(ord(num_str)+num_int)

num_str2 = "456"
print(num_str + num_str2)

num_char = 'A'
print(num_char + num_str)

print(ord(num_char))
# ord(num_char) 转为字符的ASCII码 'A'的值是65
print(ord(num_char) + num_int)

print("-------------------------------------------------------------------------------------")
print("显式类型转换")

num_char = 'A'

num_str = "abc"
num_str_a = "a"

num_str_int = "123"
num_int = 123

num_float = 1.23
num_float_str = "1.23"

num_complex = 1.23j

# ValueError: invalid literal for int() with base 10: 'A'
# print(int(num_char_A))

# ValueError: invalid literal for int() with base 10: 'abc'
# print(int(num_str_abc))

int_num_int = int(num_str_int) + num_int
print(f"{int_num_int}  \t\t type is {type(int_num_int)}")

str_num_float = float(num_float_str) + num_float
print(f"{str_num_float} \t\t  type is {type(str_num_float)}")

str_num_complex = complex(num_float_str) + num_complex
print(f"{str_num_complex} \t\t  type is {type(str_num_complex)}")

s = str(num_int)
print(f"{s} \t\t type is {type(s)}")
print(f"{num_int} \t\t  type is {type(num_int)}")

s = "12345678"
str_to_tuples = tuple(s)
str_to_list = list(s)
str_to_set = set(s)
# ValueError: dictionary update sequence element #0 has length 1; 2 is required
# str_to_dict = dict(s)
print(f"{str_to_tuples} \t\t  type is {type(str_to_tuples)}")
print(f"{str_to_list} \t\t  type is {type(str_to_list)}")
print(f"{str_to_set} \t\t  type is {type(str_to_set)}")


dict_str = {"a":1}
print(f"{dict_str} \t\t  type is {type(dict_str)}")




s = "12345678"
str_to_tuples = tuple(s)
str_to_list = list(str_to_tuples)
str_to_list.append(9)
str_to_set = set(str_to_list)
str_to_set.add(10)
print(f"{str_to_tuples} \t\t  type is {type(str_to_tuples)}")
print(f"{str_to_list} \t\t  type is {type(str_to_list)}")
print(f"{str_to_set} \t\t  type is {type(str_to_set)}")


print("-------------------------------------------------------------------------------------")
print("其他显式转换")
num = 98
num_to_char = chr(num)
char_to_num = ord(num_to_char)
num_to_hex = hex(char_to_num)
num_to_oct = oct(num)

print(f"{num} \t\t  type is {type(num)}")
print(f"{num_to_char} \t\t  type is {type(num_to_char)}")
print(f"{char_to_num} \t\t  type is {type(char_to_num)}")
print(f"{num_to_hex} \t\t  type is {type(num_to_hex)}")
print(f"{num_to_oct} \t\t  type is {type(num_to_oct)}")

image-20241217212826781

九、函数

十、标准输入输出

十一、类《Class》