Python入门系列(三)一学就会-基础数据类型

数据类型 您可以使用type()函数获取任何对象的数据类型。

x = 5 print(type(x))

数字类型
x = 1# int y = 2.8# float z = 1j# complex

Int,或integer,是一个长度不限的整数,正数或负数,不带小数。
x = 1 y = 35656222554887711 z = -3255522

浮点数,或“浮点数”是一个包含一个或多个小数的正数或负数。
x = 1.10 y = 1.0 z = -35.59

浮点数也可以是科学数字,用“e”表示10的幂。
x = 35e3 y = 12E4 z = -87.7e100

复数是用“j”作为虚部写成的
x = 3+5j y = 5j z = -5j

您可以使用int()、float()和complex()方法从一种类型转换为另一种类型
x = 1# int y = 2.8# float z = 1j# complex#convert from int to float: a = float(x)#convert from float to int: b = int(y)#convert from int to complex: c = complex(x)

Python没有生成随机数的random()函数,但Python有一个内置的模块,名为random,可用于生成随机数
import randomprint(random.randrange(1, 10))

字符串 可以使用三个引号将多行字符串指定变量
a = """Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.""" print(a)

要获得字符串的长度,请使用len()函数。
a = "Hello, World!" print(len(a))

要检查字符串中是否存在某个短语或字符,可以在中使用关键字in或者not in
txt = "The best things in life are free!" print("free" in txt)

txt = "The best things in life are free!" print("expensive" not in txt)

upper()方法以大写形式返回字符串
a = "Hello, World!" print(a.upper())

lower()方法以小写形式返回字符串
a = "Hello, World!" print(a.lower())

strip()方法从开头或结尾删除任何空格
a = " Hello, World! " print(a.strip()) # returns "Hello, World!"

replace()方法将一个字符串替换为另一个字符串
a = "Hello, World!" print(a.replace("H", "J"))

split()方法返回一个列表,其中指定分隔符之间的文本成为列表项。
a = "Hello, World!" print(a.split(",")) # returns ['Hello', ' World!']

要连接或组合两个字符串,可以使用+运算符。
a = "Hello" b = "World" c = a + b print(c)

format()方法接受传递的参数,对其进行格式化,并将其放置在占位符{}所在的字符串中
age = 36 txt = "My name is John, and I am {}" print(txt.format(age))

format()方法接受无限数量的参数,并放置在相应的占位符中:
quantity = 3 itemno = 567 price = 49.95 myorder = "I want {} pieces of item {} for {} dollars." print(myorder.format(quantity, itemno, price))

您可以使用索引号{0},以确保参数放置在正确的占位符中
quantity = 3 itemno = 567 price = 49.95 myorder = "I want to pay {2} dollars for {0} pieces of item {1}." print(myorder.format(quantity, itemno, price))

【Python入门系列(三)一学就会-基础数据类型】要在字符串中插入非法字符,请使用转义字符。
txt = "We are the so-called \"Vikings\" from the north."

布尔值 除了空值(如()、[]、{}、“、数字0和值None)之外,没有多少值的计算结果为False。当然,值False的计算结果为False。
# 下面将返回False bool(False) bool(None) bool(0) bool("") bool(()) bool([]) bool({})

Python运算符 Python算术运算符
Operator Name Example
+ Addition x + y
- Subtraction x - y
* Multiplication x * y
/ Division x / y
% Modulus x % y
** Exponentiation x ** y
// Floor division x // y
赋值运算符
Operator Example Same As
= x = 5 x = 5
+= x += 3 x = x + 3
-= x -= 3 x = x - 3
*= x *= 3 x = x * 3
/= x /= 3 x = x / 3
%= x %= 3 x = x % 3
//= x //= 3 x = x // 3
**= x **= 3 x = x ** 3
&= x &= 3 x = x & 3
\ = x \ = 3 x = x \ 3
^= x ^= 3 x = x ^ 3
>>= x >>= 3 x = x >> 3
<<= x <<= 3 x = x << 3
比较运算符
Operator Name Example
== Equal x == y
!= Not equal x != y
> Greater than x > y
< Less than x < y
>= Greater than or equal to x >= y
<= Less than or equal to x <= y
逻辑运算符
Operator Description Example
and Returns True if both statements are true x < 5 and x < 10
or Returns True if one of the statements is true x < 5 or x < 4
not Reverse the result, returns False if the result is true not(x < 5 and x < 10)
身份运算符
Operator Description Example
is Returns True if both variables are the same object x is y
is not Returns True if both variables are not the same object x is not y
成员运算符
Operator Description Example
in Returns True if a sequence with the specified value is present in the object x in y
not in Returns True if a sequence with the specified value is not present in the object x not in y
位运算符
Operator Name Description
& AND Sets each bit to 1 if both bits are 1
\ OR Sets each bit to 1 if one of two bits is 1
^ XOR Sets each bit to 1 if only one of two bits is 1
~ NOT Inverts all the bits
<< Zero fill left shift Shift left by pushing zeros in from the right and let the leftmost bits fall off
>> Signed right shift Shift right by pushing copies of the leftmost bit in from the left, and let the rightmost bits fall off

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