数据类型
您能够应用 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,负数或正数,不带小数。
x = 1
y = 35656222554887711
z = -3255522
浮点数,或“浮点数”是一个蕴含一个或多个小数的负数或正数。
x = 1.10
y = 1.0
z = -35.59
浮点数也能够是迷信数字,用“e”示意 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
您能够应用 int()、float()和 complex()办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 random
print(random.randrange(1, 10))
字符串
能够应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)
要取得字符串的长度,请应用 len()函数。
a = "Hello, World!"
print(len(a))
要查看字符串中是否存在某个短语或字符,能够在中应用关键字 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()办法以大写模式返回字符串
a = "Hello, World!"
print(a.upper())
lower()办法以小写模式返回字符串
a = "Hello, World!"
print(a.lower())
strip()办法从结尾或结尾删除任何空格
a = "Hello, World!"
print(a.strip()) # returns "Hello, World!"
replace()办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()办法返回一个列表,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!']
要连贯或组合两个字符串,能够应用 + 运算符。
a = "Hello"
b = "World"
c = a + b
print(c)
format()办法承受传递的参数,对其进行格式化,并将其搁置在占位符{}所在的字符串中
age = 36
txt = "My name is John, and I am {}"
print(txt.format(age))
format()办法承受有限数量的参数,并搁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))
您能够应用索引号{0},以确保参数搁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))
要在字符串中插入非法字符,请应用转义字符。
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。
# 上面将返回 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 |
比拟运算符
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 |