Users exchange
First, users exchange
1.1 Definitions: The user is the person to exchange computer input / input data, the computer print / output.
1.2 Purpose: To allow computers to communicate with users like human beings
>>> input("your name:")#输入数据
your name:sean
'sean'>>> print("hello world !")#输出结果
hello world !The difference between 1.3 python2 and python3
python2 input: you must declare the type of input
>>> input(">>:") >>:sean# 没有告知变量值得类型，引发错误 Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<string>", line 1, in <module> NameError: name 'sean' is not defined
>>> input(">>:")
>>:"sean"#输入的是字符串'str'
'sean'#可以正常的输出>>> input(">>:")
>>:1#输入int
1#输入int
>>> input(">>:")
>>:[1,2] #输入list
[1, 2]输出list
>>>python3 receiving user input, the user input regardless of what type, must eventually return string "str"
>>> name = input("dfhfghgf : ")
dfhfghgf : David #输入内容
>>> print(name)
David
>>> print(type(name))
<class 'str'>#字符串
>>> name = input("dfhfghgf : ")
dfhfghgf : 1234 #输入内容
>>> print(name)
1234
>>> print(type(name))
<class 'str'> #字符串
python 2 can be used with the effect of a 3 inptut raw_input python
Second, the basic data types
1.int (integer) such as age, class size, etc.
python2
In this interval [-24XXXXXXXX, 24XXXXXXXX]: variable type: int
If not in this range type: long
python3： type：int
>>> i = 29459696979939695959696#
>>> print(type(i))
<class 'int'>2.float (float) as height and weight
>>> i = 25566.2556 #带小数点
>>> print(type(i))
<class 'float'>3.str (string)
Definition: There are some descriptive information such as personal preferences, profiles, etc.
Quoted string of no distinction can '' '' But not mix can not "football '
If the string need quotes, must be fitted
For example: "ab 'cds'"
# 单引号
# s1 = 'sean'
# print(s1)
# 双引号
# s2 = "sean"
# print(s2)
# 三引号
# s3 = '''sean'''
#
# s4 = """sean"""
#
# print(s3)
# print(s4)
# s5 = 'dadada"dada"'>>> i = "David"
>>> print(type(i))
<class 'str'>#字符串python2
The nature str actually has a bit sequence of eight bits
>>> s1 = 'sean'
>>> type(s1)
<type 'str'>
>>> s1 = s1.decode("utf-8")
>>> type(s1)
<type 'unicode'>
>>> s1
u'sean'python3
In fact, the essence str unicode sequence
>>> ss1 = 'sean'
>>>
>>> type(ss1)
<class 'str'>
>>>
>>> ss1 = ss1.encode('utf-8')
>>> ss1
b'sean'
>>>
>>> type(ss1)
<class 'bytes'>1024G = 1T
1024M = 1G
1024KB = 1M
1024B = 1KB
1B = 8bit
The string can be spliced open up a new memory space, you will value the stitched into them
>>> s1 = "hello"
>>> s2 = "world"
>>> print(s1+s2) #拼接处理
helloworld4. list (list)
Definition: deposit one or more different types of values, each value with a comma (,) separated
In the count is zero-based programming
>>> t = ["abcf","大象",['read','鲜花',12344],12334]
>>> print(type(t))
<class 'list'>#列表
>>> print(t)
['abcf', '大象', ['read', '鲜花', 12344], 12334]The method takes certain values from which the following operations
>>> t = ["abcf","大象",['read','鲜花',12344],12334]
>>> print(t[2][1])
鲜花Type (dict) 5 dictionary
The method defined: by braces store data by key: value of this mapping relation to define a key value,
Each pair of keys separated by commas
>>> s1 = {"name": "Davis","age": 20, "hobby":["篮球","football","running"],"id":1235}
>>> print(type(s1))
<class 'dict'>#字典
>>> print(s1["age"])
20
>>> print(s1["hobby"])
['篮球', 'football', 'running']Boolean
The main judge right and wrong things
General does not define a separate boolean
False True
>>> print(1<2)
True#布尔类型>>> a = 2
>>> b = 2
>>> print(a==b)
TrueThe above represents the equivalent value ==
>>> a = 2
>>> b = 2
>>> print(a is b)
TrueAbove "is" meaning refer to the same id
Third, formatted output
Definition: the certain content inside a string after the replacement and then the output is formatted.
We used:
1.% s: can receive any type of variable;
2.% d: receiving a digital only type, python 3 is not used
.format
f-string (3.6 python only after a characteristic)
For example as follows:
name = input(" :") month = input(':') Phone_Bill = input(" :") Balance = input(" :") print("你好,亲爱的%s,你%s月份的话费是%s元,余额是%s元"%(name,month,Phone_Bill,Balance))#针对的%sname = input(" :") month = input(':') Phone_Bill = input(" :") Balance = input(" :") # print("你好,亲爱的%s,你%s月份的话费是%s元,余额是%s元"%(name,month,Phone_Bill,Balance)) print("你好,亲爱的%s,你%s月份的话费是%s元,余额是%d元"%(name,month,Phone_Bill,23))#针对的是%dname = input(" :") month = input(':') Phone_Bill = input(" :") Balance = input(" :") # print("你好,亲爱的%s,你%s月份的话费是%s元,余额是%s元"%(name,month,Phone_Bill,Balance)) # print("你好,亲爱的%s,你%s月份的话费是%s元,余额是%d元"%(name,month,Phone_Bill,23)) print("你好,亲爱的{},你{}月份的话费是{}元,余额是{}元".format(name,month,Phone_Bill,23))# 针对.format的使用 print("你好,亲爱的{name},你{month}月份的话费是{Phone_Bill}元,余额是{Balance}元".format(name =month,month = name,Phone_Bill = Phone_Bill,Balance = 23))# .format的一种 用法name = input(" :") month = input(':') Phone_Bill = input(" :") Balance = input(" :") print(f"你好,亲爱的{name},你{month}月份的话费是{Phone_Bill}元,余额是{Balance}元")#f的使用方法Four basic operators
4.1 Arithmetic operators
a = 9 b = 2 print(a+b) print(a-b) print(a*b) print(a/b) print(a//b) print(a%b) print(a**b)4.2 Comparison Operators
Comparison operation for comparing the two values and returns the boolean value True or
False
a = 9
b = 2
print(a==b)
print(a!= b)
print(a>b)
print(a>=b)
print(a<b)
print(a<=b)4.3 Assignment Operators
4.3.1 Augmented assignment
x = 10
# x += 1
# print(x)
# x -= 1
# print(x)
# x *= 2
# # print(x)
# x %= 3
# print(x)
x **= 3
print(x)4.3.2 Chain assignment
We want a value is assigned to multiple variables
So to operate
x = y = z = 1
print(x,y,z)4.3.3 Cross assignment
2 allows the exchange value of a variable over
a = 1
b = 2
a,b =b,a
print(a,b)4.3.4 decompression assignment
l1 = [1,2,3,4]#相当于一个压缩包
a,b,c,d = l1
print(a,b,c,d) Note: The number of variables must be the name of the equal sign on the left and right contain the same number of values, otherwise an error.
** If we want to just take the head and tail, can be used to match ** * _
l1 = [1,2,3,4,5,6,7]
#*_,a,b,c,d = l1
a,b,c,d,*_ = l1 # 用*_ 来匹配的
print(a,b,c,d)