Python It's the most popular language in the field of programming . In this paper , I will summarize Python The most common in an interview 50 A question . Each question has a reference answer , Hope to help you in 2019 Stand out in the job interview in , Get a high paying job . These interview questions involve Python Basic knowledge of 、Python Programming 、 Data analysis and Python Function library and so on .
Q1、Python What's the difference between a list and a tuple in ？
Q2、Python What is the main function of ？
Python It's an interpretative language . And C Languages are different ,Python There is no need to compile before running .
Python It's dynamic language , When you declare a variable or something like that , You don't need to declare the type of the variable .
Python Suitable for object-oriented programming , Because it allows class definition as well as composition and inheritance .Python No access instructions （ Such as C ++ Of public,private）.
stay Python in , Function is the first kind of object . They can be assigned to variables . Class is also the first kind of object
To write Python The code is fast , But it's slow .Python Allow based on C An extension of , for example numpy function library .
Python It can be used in many fields .Web Application development , automation , mathematical modeling , Big data applications and so on . It is also often used as “ glue ” Code .
Q3、Python Is it a universal programming language ？
Python Be able to write scripts , But in a general sense , It is considered to be a general programming language .
Q4、Python How to interpret language ？
Python There is no need to explain the program before it runs . therefore ,Python It's an interpretative language .
Q5、 What is? pep？
PEP representative Python Enhancement Proposal. It's a set of rules , Specify how to format Python Code for maximum readability .
Q6、 How to be in Python Manage memory in ？
python Memory management in is controlled by Python Private heap space management . all Python Objects and data structures are in the private heap . Programmers do not have access to this private heap .python The interpreter takes care of this .
Python The heap space allocation of objects is determined by Python The memory manager of . The core API Provides some tools for programmers to write code .
Python There is also a built-in garbage collector , It can reclaim all unused memory , And make it available for heap space .
Q7、Python What is the namespace in ？
A namespace is a naming system , Used to ensure that the name is unique , To avoid naming conflicts .
Q8、 What is? PYTHONPATH？
It is the environment variable used when importing the module . Whenever you import a module , You'll find it, too PYTHONPATH To check whether there are imported modules in each directory . The interpreter uses it to determine which modules to load .
Q9、 What is? python modular ？Python What are the commonly used built-in modules in ？
Python The module contains Python Code .py file . This code can be a function class or a variable . Some common built-in modules include ：sys、math、random、data time、JSON.
Q10、Python What are the local and global variables in ？
Global variables ： Variables declared outside a function or in global space are called global variables . These variables can be accessed by any function in the program .
local variable ： Any variable declared within a function is called a local variable . This variable exists in local space , Not in global space .
Q11、python Is it case sensitive ？
yes .Python It's a case sensitive language .
Q12、 What is? Python Type conversion in ？
Type conversion is the conversion of one data type to another .
int（） - Convert any data type to an integer type
float（） - Convert any data type to float type
ord（） - Convert characters to integers
hex（） - Convert integers to hexadecimal
oct（） - Convert an integer to octal
tuple（） - This function is used to convert to tuples .
set（） - This function is converted to set Post return type .
list（） - This function is used to convert any data type to a list type .
dict（） - This function is used to convert the order tuple （ key , value ） Convert to dictionary .
str（） - Used to convert integers to strings .
complex（real,imag） - This function converts real numbers to complex numbers （ The set of real Numbers , Images ） Count .
Q13、 How to be in Windows Installation on Python And set the path variable ？
To be in Windows Installation on Python, Follow these steps ：
from python After installing and downloading on the official website , Install it on your PC On . Use the following command at the command prompt to find PC Installation on PYTHON The location of ：cmd python.
Then go to advanced system settings and add a new variable and name it PYTHON_NAME And paste the copied path .
Find the path variable , Select its value and select “ edit ”.
If the value does not exist , Please add a semicolon at the end of the value , Then type. ％PYTHON_HOME％
Q14、python Whether indent is required in ？
Indentation is Python Essential . It specifies a code block . loop , class , All code in functions and so on is specified in the indent block . It's usually done with four space characters . If your code doesn't need to be indented , It will not execute accurately and will also throw errors .
Q15、Python What's the difference between arrays and lists ？
Python Arrays and lists in have the same way of storing data . however , An array can only contain a single data type element , The list can contain any data type element .
Q16、Python What is the function in ？
A function is a block of code , Only when called will it execute . To be in Python Define function in , Need to use def keyword .
Q17、 What is? __init__?
__init__ yes Python A method or structure in . Create a new class in / When an instance , This method will be called automatically to allocate memory . All classes have __init__ Method .
Q18、 What is? lambda function ？
lambda Functions are also called anonymous functions , This function can contain any number of arguments , But there can only be one statement that performs an action .
Q19、Python Medium self What is it? ？
self Is an instance or object of a class . stay Python in ,self Included in the first parameter . however ,Java This is not the case in , It's optional . It helps to distinguish between methods and properties of classes with local variables .init Methods self Variables refer to newly created objects , In other ways , It refers to the object whose method is called .
Q20、 What is? python iterator ？
Iterators are objects that can be traversed or iterated .
Q21、range＆xrange What's the difference? ？
in the majority of cases ,xrange and range Exactly the same in function . They all provide a way to generate a list of integers , The only difference is range Return to one Python List objects ,x range Return to one xrange object . That means xrange In fact, the static list is not generated at runtime . It uses what's called yielding Special techniques for creating values as needed . This technique is used with an object called a generator . So if you have a very large list , Then consider xrange.
Q22、 How to be in python Write notes in ？
Python Note in to ＃ The beginning of a character . You can also use doc-strings（ String contained in triple quotes ） Annotate .
Q23、 What is? pickling and unpickling？
Pickle The module accepts any Python Object and convert it to a string representation , And use dump The function dumps it to a file , This process is called pickling. Retrieves the original string from the stored string Python The process of an object is called unpickling.
Q24、python What is the generator in ？
The function that returns an iteratable itemset is called a generator .
Q25、 How do you capitalize the first letter of a string ？
stay Python in ,capitalize() The function can capitalize the first letter of a string . If the string already contains uppercase letters at the beginning , Then it will return the original string .
Q26、 How to convert a string to all lowercase ？
To convert a string to lowercase , have access to lower() function .
Q27、 How to be in python Comment multiple lines in ？
When commenting on multiple lines of code . All lines to be annotated should be preceded by #. You can also use shortcuts to annotate multiple lines , Just press and hold trl Key and include in each ＃ Left click on the character and type once ＃.
Q28、 What is? Python Documents in Docstrings？
Docstrings It's not really a comment , They are document strings . These document strings are enclosed in three quotation marks . They are not assigned to any variables , Therefore, it is sometimes used for annotation .
Q29、operators Medium is、not and in What's the function of each ？
Operators It's a special function , They compare one or more values and produce corresponding results . among is： When 2 The operands are true When to return to true（ for example ：“a” yes 'a'）
not： Returns the reciprocal of a Boolean value
in： Check whether an element exists in a sequence
Q30、Python in help() and dir() What is the usage of the function ？
Help() and dir() Both of these functions can be derived from Python Interpreter direct access , And used to view the merge dump of built-in functions .
help() function ：help() Function to display a document string , You can also view and modules , keyword , Properties and other related usage information .
dir() function ：dir() Function to display the defined symbol .
Q31、 When Python Exit time , Why not clear all allocated memory ？
When Python Exit time , Especially those with circular references to other objects Python Modules or objects referenced from the global namespace are not deallocated or released .
Unable to deallocate C Those parts of memory that the library keeps .
Exit time , With its own efficient cleaning mechanism ,Python Will try to deallocate / Destroy all other objects .
Q32、Python What is the dictionary in ？
Python The built-in data type in is called a dictionary . It defines a one-to-one relationship between keys and values . The dictionary contains a pair of keys and their corresponding values . Dictionaries are indexed by keys .
Q33、 How to be in python Using the ternary operator ？
Ternary operators are operators used to display conditional statements . This includes true or false value , And must evaluate the statement for it . Its basic grammar is ：
Ternary operators are operators used to display conditional statements . This includes true or false value , And must evaluate the statement for it . Its basic grammar is ：
[on_true] if [expression] else [on_false] x,y = 25,50big = x if x <y else y
Q34、 Why use * args,** kwargs？
When we are not sure how many parameters to pass to the function , Or when we want to pass the stored list or parameter tuple to the function , We use * args.** Use... When we don't know how many keyword parameters to pass to the function kwargs, Or it can be used to pass the value of the dictionary as a keyword parameter . identifier args and kwargs It's an agreement , You can also use * bob and ** billy.
Q35、len() What is the function ？
len() The function can be used to determine the string , list , The length of arrays, etc .
Q36、 stay Python in split(),sub(),subn() function .
If you want to modify a string ,Python Of “re” The module provides 3 Methods . They are ：
split() - Use the regular expression pattern to convert the given string “ Split ” Go to the list .
sub() - Finds all substrings that match the regular expression pattern , Then replace them with different strings
subn() - It is similar to sub(), And also returns a new string .
Q37、 What is a negative index , What is the function ？
Python The sequence in is indexed , It's made up of positive and negative numbers . Use positive numbers '0' As the first index ,'1' As the second index , The process continues to use .
The index of a negative number is from '-1' Start , Represents the last index in the sequence ,' - 2' As the penultimate index , The sequence moves forward like a positive number .
The negative index reference removes any newline from the string , And allow the string to be used as S [： - 1] The last character given . Negative indexes are also used to show that indexes represent strings in the correct order .
Q38、 What is? Python package ？
Python A package is a namespace that contains multiple modules .
Q39、 How to be in Python Delete files in ？
To be in Python Delete files in , You need to import OS modular . after , You need to use os.remove() function .
Q40、 What is? python Built in type ？
Python The built-in types in are as follows ： integer 、 floating-point 、 The plural 、 character string 、 Boolean et al .
