一、 python筆記基礎知識
一、 python筆記基礎知識
1.Python打印輸出
1 print("Hello Python")
2.算術運算符
# 加法運算符
1 print("4 + 2 =", 4+2)
輸出:
4 + 2 = 6
# 減法運算符
1 print("4 - 2 =", 4-2)
輸出:
4 - 2 = 2
# 乘法運算符
1 print("4 * 2 =", 4*2)
輸出:
4 * 2 = 8
# 除法運算
1 print("4 / 2 =", 4/2)
輸出:
4 / 2 = 2.0
# 除法取余
1 print
輸出:
8 % 5 = 3
# 除法取整
1 print("8 // 5 =", 8//5)
輸出:
8 // 5 = 1
# 冪運算
1 print("2 ** 3 =", 2**3)
輸出:
2 ** 3 = 8
練習:求平均數
1 print("(2+3+2+4+5) / 5 =", (2+3+2+4+5) / 5)
輸出:
(2+3+2+4+5) / 5 = 3.2
3.變量賦值
變量:在程序中存儲計算結果,計算結果可變,通過變量名訪問。
變量賦值:
1 a = 3 2print("變量a=", a)
輸出:
變量a= 3
a = 3 b = a print("變量b=", b) print("a和b的變量地址:",id(a), id(b))
輸出:
a和b的變量地址: 1353988384 1353988384
變量賦值的另一種方式:
1 x, y, z = 1, 2, 3 2 print("x = %d, y = %d, z = %d" %(x, y, z))
輸出:
x = 1, y = 2, z = 3
練習:變量和賦值運算練習
1 revenue = 1000 2 price = 20 3car = revenue / price 4 print(car) 5 # 更新revenue的值 6 revenue = revenue + 500 7 car = revenue / price 8 print(car)
輸出:
50.0
75.0
# 變量和賦值運算的另外一種方式
1 revenue += 500 2 print(revenue)
輸出:2000
1 revenue -= 500 2 print(revenue)
輸出:1500
4.整數和浮點數
# 整數
1 a = 8 2 print(type(a))
輸出:
<class ‘int‘>
# 浮點數
a = 8.0
print(type(a))
輸出:
<class ‘float‘>
註意:0.1是一個近似值
print(0.1 + 0.1 + 0.1)
輸出:
0.30000000000000004
5.bool 運算符
print(1 < 2)
輸出:
True
print(1 > 2)
輸出:
False
print(1 <= 2)
輸出:
True
print(1 >= 2)
輸出:
False
print(1 == 1)
輸出:
True
print(1 != 1)
輸出:
False
print((1 < 2) and ( 1 > 2 ))
輸出:
False
print((1 < 2) or (1 > 2))
輸出:
True
# 翻轉bool值
print(not 1 < 2)
輸出:
False
6.字符串
# 單引號和雙引號表示字符串
print("I am learning python") print(‘I am learning python‘)
# 查看字符串表示類型
str = ("I am learning python") print(type(str))
輸出:
<class ‘str‘>
# 字符串拼接
First_word = "Hello" Secend_word = "World!" print(First_word + " " + Secend_word)
輸出:
Hello World!
# 字符串重復輸出
str = (First_word + " ") * 5
輸出:
Hello Hello Hello Hello Hello
# 判斷字符串長度
print(len(str))
輸出:
30
練習:客戶信息判斷
give_name = "Luffy" middle_name = "D" family_name = "Monkey" name_length = len(give_name + middle_name + family_name) name_character_limit = 15 print(name_length <= name_character_limit)
輸出:
True
7.數據類型和數據類型轉換
# 數據類型
print(type(8))
輸出:
<class ‘int‘>
print(type(8.0))
輸出:
<class ‘float‘>
print(type(False))
輸出:
<class ‘bool‘>
print(type(True))
輸出:
<class ‘bool‘>
print(type("Hello"))
輸出:
<class ‘str‘>
# 數據類型轉換
print(float(8))
輸出:
8.0
print(int(8.0))
輸出:
8
print(int(True))
輸出:
1
print(int(False))
輸出:
0
print(float(True))
輸出:
1.0
print(float(False))
輸出:
0.0
print(type(int("8")))
輸出:
<class ‘int‘>
print(type(float("8")))
<class ‘float‘>
8.字符串常見方法
# 獲取字符串長度
print(len("Hello World!"))
輸出:
12
# 獲取字符串類型
print(type("Hello World!"))
輸出:
<class ‘str‘>
# print 打印輸出
print("Hello World!")
輸出:
Hello World!
said = "Tom is a good boy" # 判斷字符串是不是都是小寫的 print(said.islower())
輸出:
False
# 判斷字母個數 print(said.count("o"))
輸出:
4
# 查找字母在字符串中的位置 print(said.find("a"))
輸出:
7
一、 python筆記基礎知識