Common Python tips (2)

Small knowledge, big challenge! This article is participating in the creation activity of “Essential Tips for Programmers”.

In this article, we will document some of Python’s daily programming tips and use IPython to conduct interactive tests to better understand and learn some of Python’s features.

Format and print mode information

In [3] :print('success'.center(20.'='))
======success=======

In [4] :print('failed'.center(20.'='))
=======failed=======
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Else for loop

Grammar:

forvariableinIterable: the body of a loopelse: The loop ends normallyCopy the code

IPython test

# for loop
In [1] :for i in range(5) :... :print(i) ... :else:
   ...:     print('For loop completes properly')
   ...:     print(i) ... :0
1
2
3
4
forNormal end of cycle4
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Note: the else loop will not run if the loop is broken.

Let’s look at an example. Print primes up to 10.

A prime number is a natural number greater than 1 that has no other factors except 1 and itself.

for n in range(2.10) :for x in range(2, n):
        if n % x == 0:
            Covariance of # is 0 means that n has other factors
            print(n, '=', x, The '*', n // x)
            break
    else:
        No other factors of n were found
        # Loop completes normally
        print(n, It's a prime number.)
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The results show

2Is a prime number3Is a prime number4 = 2 * 2
5Is a prime number6 = 2 * 3
7Is a prime number8 = 2 * 4
9 = 3 * 3
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Comparison of mathematical expressions

In [8]: num = 5

In [9] :3 < num < 8
Out[9] :True

In [10] :6 < num < 8
Out[10] :False
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Unpacking lists and dictionaries

The list of split open a case

In [12]: a, b, c = [1.2.3]

In [13]: a, b, c
Out[13] : (1.2.3)
    
In [25]: li = [1.2.3.4.5]

In [26] :print(*li)
1 2 3 4 5

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Pass the list element as an argument to the function

In [34]: li = [1.2.3.4.5]

In [35] :def sum(*args) :. : total =0. :for i inargs: ... : total += i ... :print(total) ... : In [36] :sum(*li)
15
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The dictionary split open a case

In [27]: user_dict = { ... :'name': 'ithui'. :'sex': 'male'. :'age': 20. : } In [28]: user_info = 'My name is {name}, gender {sex}, this year {age}'.format(**user_dict)

In [29] :print(user_info) My name is Ithui, gender male, this year20At the age ofCopy the code

Function keyword arguments are automatically matched

func_params = {
    'username': 'ithui'.'mobile': '13022331752',}def query_user(username=None, mobile=None) :
    # Simulate query user information
    print(username)
    print(mobile)
    sql = """select * from user where username={} and mobile={}""".format(username, mobile)
    print(SQL) query_user func_params (* *) = = = = = = = = = = = = = = = = = = = = = = = the result as follows = = = = = = = = = = = = = = = = = = = = = = = ithui13022331752
select * from user where username=ithui and mobile=13022331752

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Take the middle element

In [15]: a, *mid, b = [1.2.3]

In [16]: mid
Out[16] : [2]

In [17]: a, *mid, b = [1.2.3.4.5.7]

In [18]: mid
Out[18] : [2.3.4.5]
    
In [21]: a, b, *mid, c, d = [1.2.3.4.5.7.8]

In [22]: mid
Out[22] : [3.4.5]    
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Gets the n largest or smallest elements in the list

In [38] :import heapq

In [39]: salarys = [5000.6000.3500.5500.7000.6500.8000]
    
In [40] :# Three largest numbers
    
In [41]: heapq.nlargest(3, salarys)
Out[41] : [8000.7000.6500]
    
In [42] :# Two smallest numbers
    
In [43]: heapq.nsmallest(2, salarys)
Out[43] : [3500.5000] 
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The tail language

✍ Code writes the world and makes life more interesting. ❤ ️

✍ thousands of rivers and mountains always love, ✍ go again. ❤ ️

✍ code word is not easy, but also hope you heroes support. ❤ ️