基础
输入输出、基本类型、变量
输入输出
python
name = input("Please enter your name.")
print("name is:", name)name is: zhangsan
整数和浮点
python
print(1, 100, -90, 0, 0xFF00, 10_000_000_000, 0xA1B2_C3D4, 1.23e9, 12.3e8, 3.14, -9.01)1 100 -90 0 65280 10000000000 2712847316 1230000000.0 1230000000.0 3.14 -9.01
字符串
python
print('I\'m "OK"!')
print(r"I\'m \"OK\"!")
print(
"""line1
lin2
lin3
"""
)I'm "OK"!
I\'m \"OK\"!
line1
lin2
lin3
布尔
python
print(True)
print(False)
print(3 > 2)
print(3 > 5)
print(True and True)
print(True and False)
print(False and False)
print(5 > 3 > 1)
print(True or True)
print(True or False)
print(False or False)
print(not True)
print(not False)
print(not 1 > 2)True
False
True
False
True
False
False
True
True
True
False
False
True
True
空值
python
print(None)None
常量
python
PI = 3.1415926585793238462643383176502
print(PI)3.1415926585793237
运算
python
print(8 / 3) # 除法
print(8 // 3) # 整除
print(8 % 3) # 取模2.6666666666666665
2
2
字符串编码
python
print("包含中文的字符串 str")
print(ord("中"), ord("国"), ord("A"))
print(chr(20013), chr(20014), chr(66))
print("\u4e2d\u6587", "中文")包含中文的字符串 str
20013 22269 65
中 丮 B
中文 中文
字节 bytes
python
print("ABC".encode("ascii"), b"ABC".decode("ascii"))
print("中文".encode("utf-8"), b"\xe4\xb8\xad\xe6\x96\x87".decode("utf-8"))
print(len("ABC"), len("中文"), len(b"ABC"), len(b"\xe4\xb8\xad\xe6\x96\x87"))
# 报错
# print('中文'.encode('ascii'))b'ABC' ABC
b'\xe4\xb8\xad\xe6\x96\x87' 中文
3 2 3 6
格式化输出
- 传统格式化输出
python
print("%2d-%02d" % (3, 1))
print("%.2f" % 3.1415926)
print("Age: %s, Gender: %s" % (25, True))
print("growth rate: %d %%" % 7) 3-01
3.14
Age: 25, Gender: True
growth rate: 7 %
- 使用 format() 格式化输出
python
print("Hello, {0}, 成绩提升了 {1:.1f}%. {2}。".format("小明", 17.125, "!"))Hello, 小明, 成绩提升了 17.1%. !。
- 使用 f-string 格式化输出
python
r = 2.5
s = 3.14 * r**2
print(f"The area of a circle with radius {r} is {s:.2f}")The area of a circle with radius 2.5 is 19.62
列表 list 和 元组 tuple
元祖 tuple：占用空间小
list 列表
python
classmates = ["Michael", "Bob", "Tracy"]
print(classmates)
print(len(classmates)) # 列表长度
print(classmates[0]) # 列表第一项
print(classmates[-1]) # 列表最后一项
classmates.append("Adam")
print("添加", classmates)
classmates.insert(1, "Jack")
print("插入", classmates)
classmates.pop()
print("删除", classmates)
classmates.pop(1)
print("删除索引为 1 的项", classmates)
classmates[1] = "Alice"
print("修改", classmates)['Michael', 'Bob', 'Tracy']
3
Michael
Tracy
添加 ['Michael', 'Bob', 'Tracy', 'Adam']
插入 ['Michael', 'Jack', 'Bob', 'Tracy', 'Adam']
删除 ['Michael', 'Jack', 'Bob', 'Tracy']
删除索引为 1 的项 ['Michael', 'Bob', 'Tracy']
修改 ['Michael', 'Alice', 'Tracy']
二维数组
python
s = ["Python", "Java", ["asp", "jsp"], "scheme"]
print(len(s))
print(s[2][1])4
jsp
tuple 元组
元组初始化后不能修改
python
classmates = ("Michael", "Bob", "Tracy")
print(classmates[1])
print(classmates[-1])
t = (1, 2)
print(t) # (1, 2)
t = ()
print(t) # ()
t = 1
print(t) # 1，因为 () 会被识别为运算符
t = (1,)
print(t) # (1,)Bob
Tracy
(1, 2)
()
1
(1,)
可"变" tuple
python
t = ("a", "b", ["A", "B"])
t[2][0] = "X"
t[2][1] = "Y"
print(t) # ('a', 'b', ['X', 'Y'])('a', 'b', ['X', 'Y'])
条件判断
if else
python
age = 20
if age >= 10:
print("your age is", age)
print("adult")
birth = int(input("birth: "))
if birth < 2000:
print("00前")
else:
print("00后")your age is 20
adult
00前
match 匹配
python
score = "B"
match score:
case "A":
print("score is A.")
case "B":
print("score is B.")
case "C":
print("score is C.")
case _:
print("score is ???.")score is B.
match 复杂匹配
python
age = 15
match age:
case x if x < 10:
print(f"< 10 years old: {x}")
case 10:
print("10 years old")
case 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18:
print("11 ~ 18 years old")
case 19:
print("19 years old")
case _:
print("not sure")11 ~ 18 years old
match 匹配列表
python
args = ["gcc", "hello.c", "world.c"]
match args:
case ["gcc"]:
print("gcc: missing source file(s)")
case ["gcc", file1, *files]:
print("gcc compile: " + file1 + ", " + ", ".join(files))
case ["clean"]:
print("clean")
case _:
print("invalid command")gcc compile: hello.c, world.c
循环
for in 循环
python
names = ["Michael", "Bob", "Tracy"]
for name in names:
print(name)
print(list(range(100)))Michael
Bob
Tracy
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99]
for in range
python
sum = 0
for i in range(101):
sum += i
print(sum)5050
while 循环
python
sum = 0
n = 99
while n > 0:
sum += n
n -= 2
print(sum)2500
break 退出循环
python
n = 1
while n <= 100:
if n > 10:
break
n += 1
print(n)11
continue 退出循环
python
n = 0
while n <= 100:
n += 1
if n % 2 == 0:
continue
print(n)1
3
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15
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25
27
29
31
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61
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65
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75
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79
81
83
85
87
89
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95
97
99
101
字典 dict
dict：空间换时间
python
names = ["Michael", "Bob", "Tracy"]
scores = [95, 85, 75]
d = {"Michael": 95, "Bob": 85, "Tracy": 75}- dict 中，字符串、整数都是不可变的，因此可以作为 key；
- list 由于是可变的，因此不可以作为 key；
python
# 会报错
# key = [1, 2, 3]
# d[key] = 'a list'查看 dict 中的 value
python
print(d["Michael"])95
判断 dict 中 key 是否存在
python
print("Alice" in d, "Michael" in d)
print(d.get("Alice", None), d.get("MIchael", None))False True
None None
删除 dict 中某个 key
python
d.pop("Michael")
print("dict is:", d)dict is: {'Bob': 85, 'Tracy': 75}
集合 set
python
s = {1, 2, 3} # 等价于 set([1, 2, 3])
print(s){1, 2, 3}
去重
python
s = {1, 2, 3, 3, 3, 2, 2}
print(s){1, 2, 3}
添加
python
s.add(4)
print(s){1, 2, 3, 4}
删除
python
s.remove(3)
print(s){1, 2, 4}
交集 & 和并集 |
python
s1 = {1, 2, 3}
s2 = {2, 3, 4}
print(s1 & s2) # {2, 3}
print(s1 | s2) # {1, 2, 3, 4}{2, 3}
{1, 2, 3, 4}
不可变对象 str
list 可变对象
python
a = ["c", "b", "a"]
a.sort()
print(a)['a', 'b', 'c']
str 不可变对象
python
a = "abc"
b = a.replace("a", "A") # replace 作用在 'abc' 上，而不是变量 a 上
print(a, b)abc Abc