Summarize some Python programming skills-Python Tutorial-php.cn

Summarize some Python programming skills

伊谢尔伦

Release： 2017-06-28 13:17:14

Original

1408 people have browsed it

This article mainly introduces some programming skills for Python beginners. They are all based on some basic programming habit suggestions. Friends in need can refer to

Exchange Variables

x = 6
y = 5
 
x, y = y, x
 
print x
>>> 5
print y
>>> 6

Copy after login

if statement in line

print "Hello" if True else "World"
>>> Hello

Copy after login

Connection

The last way below is very cool when binding two objects of different types.

nfc = ["Packers", "49ers"]
afc = ["Ravens", "Patriots"]
print nfc + afc
>>> [&#39;Packers&#39;, &#39;49ers&#39;, &#39;Ravens&#39;, &#39;Patriots&#39;]
 
print str(1) + " world"
>>> 1 world
 
print `1` + " world"
>>> 1 world
 
print 1, "world"
>>> 1 world
print nfc, 1
>>> [&#39;Packers&#39;, &#39;49ers&#39;] 1

Copy after login

Number skills

#除后向下取整
print 5.0//2
>>> 2
# 2的5次方
print 2**5
>> 32

Copy after login

Pay attention to the division of floating point numbers

print .3/.1
>>> 2.9999999999999996
print .3//.1
>>> 2.0

Copy after login

Numeric values Compare

This is one of the few multilingual I have seen such a great simple method

x = 2
if 3 > x > 1:
 print x
>>> 2
if 1 < x > 0:
 print x
>>> 2

Copy after login

Iterate over two lists simultaneously

nfc = ["Packers", "49ers"]
afc = ["Ravens", "Patriots"]
for teama, teamb in zip(nfc, afc):
  print teama + " vs. " + teamb
>>> Packers vs. Ravens
>>> 49ers vs. Patriots

Copy after login

Indexed list iteration

teams = ["Packers", "49ers", "Ravens", "Patriots"]
for index, team in enumerate(teams):
 print index, team
>>> 0 Packers
>>> 1 49ers
>>> 2 Ravens
>>> 3 Patriots

Copy after login

List comprehension

Given a list, we can brush out the even-numbered list method:

numbers = [1,2,3,4,5,6]
even = []
for number in numbers:
 if number%2 == 0:
  even.append(number)

Copy after login

transforms into the following:

numbers = [1,2,3,4,5,6]
even = [number for number in numbers if number%2 == 0]

Copy after login

Isn’t it awesome, haha.

Dictionary comprehension

Similar to list comprehension, a dictionary can do the same job:

teams = ["Packers", "49ers", "Ravens", "Patriots"]
print {key: value for value, key in enumerate(teams)}
>>> {&#39;49ers&#39;: 1, &#39;Ravens&#39;: 2, &#39;Patriots&#39;: 3, &#39;Packers&#39;: 0}

Copy after login

Initialize the value of the list

items = [0]*3
print items
>>> [0,0,0]

Copy after login

Convert list to string

teams = ["Packers", "49ers", "Ravens", "Patriots"]
print ", ".join(teams)
>>> &#39;Packers, 49ers, Ravens, Patriots&#39;

Copy after login

Get elements from dictionary

I admit that the try/except code is not elegant, but here is a simple method, try to find the key in the dictionary, if the corresponding alue is not found, the second parameter will be used to set its variable value.

data = {&#39;user&#39;: 1, &#39;name&#39;: &#39;Max&#39;, &#39;three&#39;: 4}
try:
 is_admin = data[&#39;admin&#39;]
except KeyError:
 is_admin = False
1

Copy after login

Replace with this:

data = {&#39;user&#39;: 1, &#39;name&#39;: &#39;Max&#39;, &#39;three&#39;: 4}
is_admin = data.get(&#39;admin&#39;, False)

Copy after login

Get a subset of the list

Sometimes, you only want a subset of the list elements, here are some ways to get a subset of a list.

x = [1,2,3,4,5,6]
#前3个
print x[:3]
>>> [1,2,3]
#中间4个
print x[1:5]
>>> [2,3,4,5]
#最后3个
print x[-3:]
>>> [4,5,6]
#奇数项
print x[::2]
>>> [1,3,5]
#偶数项
print x[1::2]
>>> [2,4,6]

Copy after login

60 characters to solve FizzBuzz

Some time ago Jeff Atwood promoted a simple programming exercise called FizzBuzz. The question is quoted as follows ：

Write a program that prints the numbers 1 to 100. Multiples of 3 print "Fizz" to replace this number. Multiples of 5 print "Buzz". For numbers that are both multiples of 3 and 5, print "FizzBuzz".

Here is a short, interesting way to solve this problem:

for x in range(101):print"fizz"[x%3*4::]+"buzz"[x%5*4::]or x

Copy after login

Collection

In addition to python’s built-in data In addition to type, the collection module also includes some special use cases. Counter is very practical in some situations. If you participated in this year's Facebook HackerCup, you can even find its practicality.

from collections import Counter
print Counter("hello")
>>> Counter({&#39;l&#39;: 2, &#39;h&#39;: 1, &#39;e&#39;: 1, &#39;o&#39;: 1})

Copy after login

Iteration tools

Like the collections library, there is also a library called itertools, which can really solve certain problems efficiently. One use case is to find all combinations, which tells you all the possible combinations of elements in a group

from itertools import combinations
teams = ["Packers", "49ers", "Ravens", "Patriots"]
for game in combinations(teams, 2):
 print game
>>> (&#39;Packers&#39;, &#39;49ers&#39;)
>>> (&#39;Packers&#39;, &#39;Ravens&#39;)
>>> (&#39;Packers&#39;, &#39;Patriots&#39;)
>>> (&#39;49ers&#39;, &#39;Ravens&#39;)
>>> (&#39;49ers&#39;, &#39;Patriots&#39;)
>>> (&#39;Ravens&#39;, &#39;Patriots&#39;)

Copy after login

False == True

than This is a very interesting thing from a practical technical point of view. In python, True and False are global variables, so:

False = True
if False:
 print "Hello"
else:
 print "World"
>>> Hello

Copy after login

The above is the detailed content of Summarize some Python programming skills. For more information, please follow other related articles on the PHP Chinese website!