1. Built-in functions
Some functions that come with python can be used directly
print (max(111,12)) #take the maximum value print (min(12,23)) #take the minimum value print (abs(-1)) #take the absolute value print (round(11.23454,2)) #take a few Digit decimals print (sorted([1,23,45,66,33,2])) #Sort , can be used for dictionary sorting dic = {1:2,3:4,5:6 } print (sorted(dic.items ())) #Sort by the key of the dictionary print (sorted(dic.items(),key = lambda x:x[1])) #Sort by the value of the dictionary print (id(dic)) #See the memory address print ( type(dic)) #See the data type print ()#Print input() #Input list() #Turn list, string to list with .split set() #Turn set str() #Turn string, list to string with .join dict() #Turn dictionary int ( ) #turn int float() #turn float type len() #take length
print (dir( ' abc ' )) #The way to view the string, don't look at the _xx_ print (dir({})) #Print the callable method of the incoming object print (all([1,2,3 ,4])) #Determine whether the values in the iterable object are all true print (any([0,1,2,3,4,])) #Determine whether one of the values in the iterable object is true print (bin(10)) #Decimal to binary, 0b1010 print (bin(10).replace( ' 0b ' , '' )) # 1010 print (hex(111)) #Number to hexadecimal print (oct( 111)) #Convert the number to octal print (bool( 's ' )) #Convert an object to a boolean type print (bytearray( ' abcd ' ,encoding= ' utf-8 ' )) # Convert a string to a modifiable bytes,bytearray(b'abcd') print ( chr(69)) #Print the ascii corresponding to the number print (ord( ' E ' )) #Print the ascii code corresponding to the string exec ( ' def a():print("I am a") ' ) #Execute python code print (eval( ' [] ' )) #Execute python code, only simple, define data types and operations [],{} a = eval(' 1+2 ' ) print (a) print (filter( lambda x: x > 5, [12, 3, 12, 2, 1, 2, 35])) #Filter the following iterative objects according to the previous method print (map( lambda x: x > 5, [1, 2, 3, 4, 5, 6 ])) print ( frozenset ({1, 2, 3, 3})) #define an unmodifiable set print (globals ()) #Return all variables in the program, what is returned is a dictionary print (locals()) #Return local variables print (hash( ' aaa ' )) #Hash a string into a number
Second, json processing
JSON is a data type of key-value data structure common to all languages, much like a dictionary in python
json file to python dictionary
python dictionary to string and write to json file
3. Module
A module is actually a python file
1. Standard modules, standard packages
#python comes with these modules,
import string, random, datetime, os, json that can be used directly by import
2. Third-party modules, some modules written by others, You have to install it before you can use
#1, the fool-like
pip install pymysql
1. What to do if there is no pip command:
1. Click python console in pycharm
2. Find the python installation directory
3, then add the scripts directory under the installation directory to Go to the environment variable and you can
ps: add 2 to the environment variable in the PATH
, Unknown or unsupported command 'install' How to solve this question
1. Open C:\strawberry\perl\bin\
2. Put all pip in this directory Change to another name , this has no effect on
others Package 1. Unzip the compressed package 2. Enter the unzipped folder 3. Run python setup.py install on the command line 3. Write your own python file