Catalog
keyword ：
class: Defining classes
Built in functions ： Consistent with the call of the defined function
Common methods ： String method
List common methods ： It can store all kinds of data types
Methods of adding, deleting, looking up and modifying dictionaries
Several other methods commonly used in dictionaries
Method ： Use of methods ： object . Method name ( Parameters )
False:bool data type
True：bool data type
None： Indicates that the content of the data is empty
and： Logical operators ： And
or： Logical operators ： or
not： Logical operators ： Not
in： Identity operator , Determine whether the variable is in the sequence
is : member operator , Determine whether the variable is an instance of a class
del: Delete the value of a variable or sequence
assert: Sort the list , The default order is from small to large , Ascending , Add parameters reverse=True, Sort in descending order
with： simplify Python The sentence of
pass： Said by ( Usually used to occupy space )
if elif else： conditional
while： Conditional statements
for： Loop statement
break: End cycle , Jump out of the loop
continue: Terminate the current cycle , Start the next cycle
def: Keywords defined by the function
return： Define the function to return the calculation result , To receive
global： Define global variables
nonlocal： Modify the value of the local variable of the external function inside the nested function
lambda： Defining anonymous functions
yield： Used to return values from a function in turn
import： Define modules
from： For importing modules , And import Use a combination of
as: For type conversion
raise： Exception throw operation
try： For exception statements
except： For exception statements
finally： For exception statements
print : Output
input : Input
type : View data type
id : Get the memory address of the data
range : Generate the data
len : Get the length of the data ( The total number of elements )
int、float 、bool 、str、list、tuple、dict、set： Represents the corresponding data type
eval: Identify... In a string python expression
eval： You can convert string types to lists or primitives
join String splicing , Convert list to string
find Find element location
count Find the number of elements
replace Replace character
split String segmentation , Convert string to list
format Format output The traditional way ：%
upper Capitalize the letters
lower Put the letters in lowercase
Variable data type , The most used data storage methods
Take value by subscript , List method
increase ：
append Add data to the list ( At the end of ）
insert Insert data through the specified location
extend You can add multiple pieces of data to the list at one time ( At the end of ）
Delete ：
remove Delete the element specified in the list
pop Specify the subscript position to delete , Delete the last element of the list by default
clear clear list
del Keyword deletion , Specifies that the subscript is deleted , Method can be deleted
Inquire about ：
index Subscript method of query list
count Get the number of elements
Be careful ： The query method needs variables to receive
modify ： Find the corresponding element through the subscript position and modify it
li3[5],li3[6] = 111,222
other ：
copy Copy list
sort Sort , The default order is from small to large , Ascending , Add parameters reverse=True, Sort in descending order
reverse Reverse the list
# Add elements to the dictionary
# Assignment by key dic[key] = value
dic["age"] = 18
print(dic)
# Modify elements in the dictionary ( In the dictionary key Is the only one. , Can't repeat ),
dic["age"] = 188
# summary ： Dictionaries add and modify elements , nothing key Then increase , If there is one, change it
# Look up elements in the dictionary
# Use the key to find the corresponding value （ When the key you are looking for does not exist , Will report a mistake )
n = dic["name"]
print(n)
# The second kind ：dic.get(key)（ When the key you are looking for does not exist , The return is None)
n = dic.get('name')
print(n)
# Delete element from Dictionary
dic1 = {'aa':11,'bb':22,'cc':33}
# pop Method : Specify the key to delete the key value pair
print(dic1.pop("aa"))
print(dic1)
# popitem: Delete the last key value pair in the dictionary (python3.6 Start )
dic1.popitem()
print(dic1)
# del keyword To delete
del dic1['bb']
print(dic1)
dic2 = {'aa': 11, 'bb': 22, 'cc': 33}
# keys: Get all keys
print(list(dic2.keys()))
# values： Get all values
print(list(dic2.values()))
# items： Get all key value pairs , Each key value pair is a primitive form
print(list(dic2.items()))
# How to combine two dictionaries ：update,dic1 Update to dic3 Go inside
dic3.update(dic1)
print(dic3)
# Add multiple key value pairs to the dictionary
dic3.update({"ff": 11, "dd": 99})
print(dic3)
# How to combine two dictionaries ：update,dic1 Update to dic3 Go inside
dic3.update(dic1)
print(dic3)
# Add multiple key value pairs to the dictionary
dic3.update({"ff": 11, "dd": 99})
print(dic3)
function 、 keyword 、 Differences in the use of methods
function ：
The function is ： Function name ()
print("hello python")
input(" account number ")
keyword
Keyword use ： Keyword name python expression ( There are no brackets )
del li[0]
if Conditional statements
return a+b
for example ： List method
li = [11,22,33]
li.append()
'''
```
