First, the procedures and user interaction
The user interaction is input to the computer people / input data, the computer print output, the nature / interaction is input, the output
1, input input
input function and in python3 in python2 there are some differences:
# In python3 in, input function will wait for user input, the user input any type of content will become a string, and then assigned to the variable name on the left >>> name = the INPUT ( " Please enter your name: " ) Please enter your name: abc # name = "abc" >>> the INPUT = password ( " Please enter your password: " ) Please enter your password: 123 # password = "123" >>> of the type (name) < class ' str ' > >>> type(password) <class 'str'> # In python2 in, input feature requires the user to input a specific data type # but there are a python3 and the same usage is raw_input >>> name = the INPUT ( " Please enter your name: " ) Please enter your name: abc Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<string>", line 1, in <module> NameError: name 'abc' is not defined >>> name = input("请输入你的名字：") Please enter your name: " abc " >>> name ' abc ' >>> of the type (name) <of the type ' str ' > Password = the INPUT >>> ( " Please enter your password: " ) Please enter your password: 123 >>> type(password) <type 'int'> The INPUT name = >>> ( " Please enter your name: " ) Please enter your name: [ 1,2 ] >>> type (name) <type ' List ' > >>> name = raw_input("名字：") 名字：[1,2] >>> type(name) <type 'str'>
2, the output print
Some content formatted output is to replace the inside of a string before outputting
Output format in three ways:
a, placeholder% d,% s
# % S placeholder may receive any type of data # % D can only receive digital placeholder >>> Print ( ' Your name is% s, your age d% ' % ( ' abc ' , 18 )) Your name is abc, your age is 18
b, using the format method
# The format according to the received data sequence before and after >>> Print ( ' your name: {}, your age: {} ' .format ( ' ABC ' , 18 is )) Your name: abc, your age: 18 # The format data received in a corresponding relationship >>> name = ' ABC ' >>> age = 18 >>> >>> Print ( ' Your age: {age}, your name: {name} ' .format (name = name, Age = Age)) Your Age: 18 Your name: abc
c, f-string using the method of
# f"{}"方法 >>> name = 'abc' >>> age = 18 >>> Print (f " your age {age}, your name, name} { " ) Your age 18, your name abc
Second, the basic data types
Learn variable is to allow computers to like people to remember things in a certain state, and the state of things there are a variety of types, such as a person's height, weight, age, position, etc., and will have different data variables Types of
Data : description, measure the state of the data
Type : different things require different types of storage
1, digital type
a, int int
age = 18 essentially: age = int (18)
# In python3, regardless of how much the value of integer data types are int >>> a = 11111111111111111111111111111111 >>> type(a) <class 'int'> # In python2 in the range [-24xxxxxxxx, 24xxxxxxxx]: int # not in this range: long >>> a = 1111111 >>> type(a) <type 'int'> >>> a = 1111111111111111111111111111111111111 >>> type(a) <type 'long'>
b, float type floating-point
weight = 65.4 nature: weight = float (65.4)
>>> weight = 65.4 >>> type(weight) <class 'float'>
2, str string type
Definition: keep some descriptive information, keep personal interests, personal profiles
Quoted string is no difference, but can not be mixed
, if needed quoted string, it must be nested
Essence s1 = 'abc' is: s1 = str (abc)
# To python3 STR sequences are really Unicode sequence >>> SS1 = ' ABC ' >>> type (SS1) < class ' STR ' > >>> ss1 = ss1.encode('utf-8') >>> ss1 b'abc' >>> type(ss1) <class 'bytes'> # Python2 STR sequences are really 8-bit bit sequence >>> S1 = ' ABC ' >>> type (S1) <type ' STR ' > >>> s1 = s1.decode("utf-8") >>> s1 u'abc' >>> type(s1) <type 'unicode'>
The string can be the + operator, the effect is to stitching together two strings
>>> s1 = 'abc' >>> s2 = 'def' >>> s3 = s1 + s2 >>> s3 'abcdef'
3, list the type of list
The presence of one or more types of values, index list index starting from 0
>>> s1 = ['a',12,['b','c','d',18]] >>> s1[1] 12 >>> s1[2][0] 'b'
4, dict dictionary
The method defined: by braces store data by key: value of this key-defined mapping relationship
Each key-value pairs are separated by brackets
>>> d1 = {"name":'abc',"age":19}
>>> type(d1)
<type 'dict'>
D1 >>> [ ' name ' ]
' ABC '
# dictionary can be nested
>>> D2 = { " name " : ' ABC ' , " Age " :. 19, " Hobby " : [ ' D ' , ' E ' ] }
>>> D2 [ " Hobby " ] [. 1] # to take a second hobby E
' E '
5, bool boolean
Right or wrong judgment of things mainly used, generally not separately defined
>>> 1<2 True >>> a = 277 >>> b = 277 A == b >>> # equal sign is comparable value True >>> A IS b # IS address comparison is False “““ The values are equal, id not necessarily equal Case of equal id, value must be equal ”””
Third, the basic operators
1, arithmetic
+、-、*、/
// divisible
% Modulus
** Index
2, the assignment operator
+=、-=、*=、/=
>>> a = 1 = A +. 1 >>> # similar. 1 + A = A >>> A 2 >>> b = 5 B >>> -. 1 = # similar to B = B -. 1 >>> B . 4 >>> c = 2 C * = 2 >>> # similar = C * 2 C >>> C . 4 >>> d = 2 D >>> / 2 = # similar to D = D / 2 >>> D . 1
3, chain assignment
>>> x = y = z = 1 >>> print(x,y,z) (1, 1, 1)
4, cross assignment
>>> a = 1 >>> b = 2 >>> print(a,b) ( 1, 2 ) # exchanging a, b values >>> a, b = B, A >>> Print (a, b) (2, 1)
5, decompression assignment
>>> s1 = [1,2,3,4,5] >>> a,b,c,d,e = s1 >>> print(a,b,c,d,e) ( 1, 2, 3, 4, 5 ) # when the number of the need to assign less than the length of the list, by default represents _ * >>> S2 = [1,2,3,4,5 ] >>> A, B, C, _ = * S2 >>> Print (A, B, C) . 1 2. 3 >>> *_,e,d,f = s2 >>> print(e,d,f) 3 4 5 >>>
6, the logic operation
And, or, not
and、or、not