Python Grammar 02

Primer

We mainly learned on a python as a programming language, and today it is about learning content on user interaction, data types and operators in terms of

User interaction

What is the user interaction?

User interaction is human input data into the computer (input), computer output (print)

A very simple example, we enter the following code in the pycharm

the INPUT = age ( " Please enter the Age: " )    # to enter data into a computer 
Print (of the type (age))       # let the computer age output data types

At this time, the computer will receive user input, in fact, no matter what type of data input, the final return must be a string (str)

 

 

 PS: python2 must declare the type of input you entered, python2 the raw_input and input in the same python3

 Formatted output

The something inside a string and then replaced after the output is formatted output.

How to format the output?

1, placeholders, such as:% s,% d:

# % S placeholder: You can receive any type of value 
# % d placeholders: only receive a number, if not a number will error 
Print ( ' Dear% s% s Hello you sign up month course has been successful! , tuition D% ' % ( ' Tom ' , 10, 18000))

The output is:

 

 

 2、format

Ado, a direct example:

# .Fomat usage 
name = ' Tom ' 
Age = ' 18 is ' 
Print ( " My name IS {}, {} IS My Age " .format (name, Age))
 # can also be used the following methods 
Print ( " My name IS name} {, My Age Age {IS} " .format (name = name, Age Age =))

The results are output

 

 

 3, f-string (this is the only version will be after the python3.6)

# f-string的用法
name = 'Tom'
age = '18'
print(f" my name is {name}, my age is {age}")

 

 

 type of data

1, integer int (define: 'except X' telephone number, ID number, age)

PS: Long long: only python 2 has a long integer, long range -2147483647 2147483647, i.e. -2 ^ 31 to 2 ^ 31-1

age = 18  # age=int(18)

print(id(age))
print(type(age))
print(age)

140718798304048
<class 'int'>
18

2, float folt (definable weight, height, salary)

salary = 2.1  # salary=float(2.1)
print(id(salary))
print(type(salary))
print(salary)

2035028452208
<class 'float'>
2.1

3, the string str (define loving, personal profiles)

name1 = 'Tom'
name2 = "Sam"
print(id(name1))
print(type(name1))
print(name1)

1398355144944
<class 'str'>
Tom

PS: Here mention

　　str nature python 2 has in fact a sequence of 8-bit bit

　　str nature python 3 is actually a unicode sequence

　　Use indistinguishable quoted string (single lead, double lead, triple quotes can), but can not mix

　　If you need to have a quoted string, you must use a nested

　　String concatenation that has opened up a new space, into the data

4, the list of list (stored values ​​of one or more different types)

　　Any type of value are separated by a comma within [].

hobby = 'read'
hobby_list = [hobby, 'run', 'girl']
print(id(hobby_list))
print(type(hobby_list))
print(hobby_list)

2855587238472
<class 'list'>
['read', 'run', 'girl']

Deposit is not an end, is taking aim, we introduce the method list index value, bearing in mind the index number from zero.

= hobby_list [ ' Read ' , ' RUN ' , ' Girl ' ]
 # index number 012 
# Remove second interested 
Print (hobby_list [. 1])

run

= hobby_list [ ' Read ' , ' RUN ' , [ ' girl_name ' , 18 is, ' Shanghai ' ]]
 # removed girl age 
Print (hobby_list [2] [. 1])

18

5, the dictionary dict

effect

A plurality of values ​​used to access, in accordance with key: value of the stored-value mode, may not take the time to go to the index value by the key, key has a function of descriptive value. Store a variety of types of data and more data when you can use a dictionary.

usage

{} In the plurality of elements separated by commas, each element is key: value format, the format in which the value is an arbitrary data type, since the key has a function descriptive, the key is usually a string type.

# Dictionary set list 
USER_INFO = { ' name ' : ' Tom ' , ' Gender ' : ' MALE ' , ' Age ' : 20 is ,
              ' company_info ' : [ ' Oldboy ' , ' Shanghai ' , 50 ]}
 Print (USER_INFO [ ' name ' ])
 Print (USER_INFO [ ' company_info ' ] [0])

tom
oldboy

# Dictionary sleeve dictionary 
USER_INFO = { ' name ' : ' Tom ' , ' Gender ' : ' MALE ' , ' Age ' : 20 is, ' company_info ' : {
     ' c_name ' : ' Oldboy ' , ' c_addr ' : ' Shanghai ' , ' c_num_of_employee ' : 50 }}

print(user_info['name'])
print(user_info['company_info']['c_name'])

tom
oldboy

6, Boolean type bool

Mainly for judging right or wrong things, only two values: Ture and False, not separately defined general Boolean type

# Boolean type 
A. 1 = 
B =. 1
 Print (A == B)     # == is the comparison value 
Print (A IS B)     # IS is compared id

True
True

PS: a case where the values ​​are equal, id not necessarily the same

　　 The same id, it necessarily the same

Operators

Arithmetic Operators

# Arithmetic operators 
print (. 1 + 2)     # plus 
print (. 1 - 2)     # Save 
print (2. 1 *)     # by 
print (. 1/2)     # inter 
print (10 //. 3)   # divisible only rounded 
print (10% 3)    # modulo 
Print (10 ** 3)     # power

Output:

3
-1
2
0.5
3
1
1000

 

 

 Comparison Operators

# Comparison operators 
A = 10 
B = 20 is
 Print (A == B)        # Analyzing equal 
Print (A! = B)        # judged not equal 
Print (A> B)         # judged greater than 
Print (A> = B)        # judged greater than equals 
Print (A <B)         # Analyzing less than 
Print (A <= B)        # Analyzing less

Output:

False
True
False
False
True
True

 

 

 Assignment Operators

age = 19
age = age + 1
print(age)

20

=. 19 Age 
Age + = #. 1 plus equals
 Print (Age)

20

=. 19 Age 
Age * # = 10 by equal
 Print (Age)

190

 

 Chain assignment

# Chain assignment 
X. 1 = 
Y =. 1 
Z =. 1 
X = Y = Z
 Print (X, Y, Z)

1 1 1

Cross assignment

# CROSS assignment 
A =. 1 
B = 2
 Print (A, B)
a, b = b, a
print(a, b)

1 2
2 1

Decompression assignment

# Decompression assignment 
L1 = [. 1, 2,. 3,. 4 ]
L2 = [1, 2, 3, 4, 5, 6 ]
A, B, C, D = L1
 Print (A, B, C, D)            # At this time, if the print error would l2 
# * _ accept overflow elements 
A, B, C, D, * _ = l2
 Print (A , B, C, D, * _)
 Print (_ *, A, B, C, D)

1 2 3 4
1 2 3 4 5 6
5 6 1 2 3 4

Logical Operators

and: there is a return False, the whole equation are False

or: There is a return Ture, the whole equation are Ture

not: not true (inverted)

# Logical operators 
Print (10 <20 is and 20 is> 30 and 30 <40)       # a return False, whole expression are False 
Print (10> 20 is or 20 is> 30 or 30 <40)         # has a return Ture , the whole equation are Ture

false
True