Python language 3.x is completely incompatible with the future. As a result, libraries that we can use normally in python2.x cannot be used in python3. For example, mysqldb
Currently, MySQLdb does not support python3.x and Python3.x. Solutions for connecting to MySQL include: oursql, PyMySQL, myconnpy, etc.
Let’s talk about how to install and use pymysql in python3. I will talk about the other two solutions later.
1.pymysql installation
pymysql is a replacement for mysqldb in python3 environment. Enter the command line and use pip to install pymysql
pip install pymysql3
2.pymysql use
If you want to use mysqldb, then directly at the beginning of the py file Just add the following two lines of code.
#引入pymysql import pymysql #当成是mysqldb一样使用,当然也可以不写这句,那就按照pymysql的方式 pymysql.install_as_MySQLdb()
3. pymysql query example
__author__ = 'pythontab.com' #导入pymysql的包 import pymysql try: #获取一个数据库连接,注意如果是UTF-8类型的,需要制定数据库 conn=pymysql.connect(host='localhost',user='pythontab',passwd='pythontab',db='pythontab',port=3306,charset='utf8') cur=conn.cursor()#获取一个游标 cur.execute('select * from user') data=cur.fetchall() for d in data : #注意int类型需要使用str函数转义 print("ID: "+str(d[0])+' 用户名: '+d[1]+" 注册时间: "+d[2]) cur.close()#关闭游标 conn.close()#释放数据库资源 except Exception :print("查询失败")

TomergelistsinPython,youcanusethe operator,extendmethod,listcomprehension,oritertools.chain,eachwithspecificadvantages:1)The operatorissimplebutlessefficientforlargelists;2)extendismemory-efficientbutmodifiestheoriginallist;3)listcomprehensionoffersf

In Python 3, two lists can be connected through a variety of methods: 1) Use operator, which is suitable for small lists, but is inefficient for large lists; 2) Use extend method, which is suitable for large lists, with high memory efficiency, but will modify the original list; 3) Use * operator, which is suitable for merging multiple lists, without modifying the original list; 4) Use itertools.chain, which is suitable for large data sets, with high memory efficiency.

Using the join() method is the most efficient way to connect strings from lists in Python. 1) Use the join() method to be efficient and easy to read. 2) The cycle uses operators inefficiently for large lists. 3) The combination of list comprehension and join() is suitable for scenarios that require conversion. 4) The reduce() method is suitable for other types of reductions, but is inefficient for string concatenation. The complete sentence ends.

PythonexecutionistheprocessoftransformingPythoncodeintoexecutableinstructions.1)Theinterpreterreadsthecode,convertingitintobytecode,whichthePythonVirtualMachine(PVM)executes.2)TheGlobalInterpreterLock(GIL)managesthreadexecution,potentiallylimitingmul

Key features of Python include: 1. The syntax is concise and easy to understand, suitable for beginners; 2. Dynamic type system, improving development speed; 3. Rich standard library, supporting multiple tasks; 4. Strong community and ecosystem, providing extensive support; 5. Interpretation, suitable for scripting and rapid prototyping; 6. Multi-paradigm support, suitable for various programming styles.

Python is an interpreted language, but it also includes the compilation process. 1) Python code is first compiled into bytecode. 2) Bytecode is interpreted and executed by Python virtual machine. 3) This hybrid mechanism makes Python both flexible and efficient, but not as fast as a fully compiled language.

Useaforloopwheniteratingoverasequenceorforaspecificnumberoftimes;useawhileloopwhencontinuinguntilaconditionismet.Forloopsareidealforknownsequences,whilewhileloopssuitsituationswithundeterminediterations.

Pythonloopscanleadtoerrorslikeinfiniteloops,modifyinglistsduringiteration,off-by-oneerrors,zero-indexingissues,andnestedloopinefficiencies.Toavoidthese:1)Use'i


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