Some tips for beginners in Python

Here are some of the python practical tips and tools I've collected in recent years that I hope will help you.

Swap variables

x = 6

y = 5

X, y = y, X

Print X

>>> 5

Print Y

>>> 6

If statement in row

Print "Hello" if True else "world"

>>> Hello

Connection

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

NFC = ["Packers", "49ers"]

AFC = ["Ravens", "patriots"]

Print NFC + AFC

>>> [' Packers ', ' 49ers ', ' Ravens ', ' patriots ']

Print str (1) + "World"

>>> 1 World

print ' 1 ' + "world"

>>> 1 World

Print 1, "World"

>>> 1 World

Print NFC, 1

>>> [' Packers ', ' 49ers '] 1

Digital tricks

#除后向下取整

Print 5.0//2

>>> 2

# 2 of the 5-time Square

Print 2**5

>> 32

Note the division of floating-point numbers

Print. 3/.1

>>> 2.9999999999999996

Print. 3//.1

>>> 2.0

Numerical comparison

This is one of the few simple methods I've seen in many languages.

x = 2

If 3 > x > 1:

Print X

>>> 2

If 1 < x > 0:

Print X

>>> 2

Iterate over two lists at a time

NFC = ["Packers", "49ers"]

AFC = ["Ravens", "patriots"]

For TeamA, teamb in Zip (NFC, AFC):

Print TeamA + "vs." + Teamb

>>> Packers vs. Ravens

>>> 49ers vs. Patriots

List Iteration with index

Teams = ["Packers", "49ers", "Ravens", "patriots"]

For index, team in enumerate (teams):

Print index, Team

>>> 0 Packers

>>> 1 49ers

>>> 2 Ravens

>>> 3 Patriots

List-derived

Given a list, we can swipe to select the even-numbered table method:

numbers = [1,2,3,4,5,6]

even = []

For number in numbers:

If number%2 = = 0:

Even.append (number)

Into the following:

numbers = [1,2,3,4,5,6]

even = [number for number in numbers if number%2 = = 0]

is not very cow, haha.

Dictionary derivation

Similar to list derivation, dictionaries can do the same thing:

Teams = ["Packers", "49ers", "Ravens", "patriots"]

Print {Key:value for value, key in enumerate (teams)}

>>> {' 49ers ': 1, ' Ravens ': 2, ' Patriots ': 3, ' Packers ': 0}

Initialize the value of the list

Items = [0]*3

Print items

>>> [0,0,0]

The list is converted to a string

Teams = ["Packers", "49ers", "Ravens", "patriots"]

Print ",". Join (teams)

>>> ' Packers, 49ers, Ravens, Patriots '

Get elements from a dictionary

I admit that the try/except code is not elegant, but there is an easy way to try to find the key in the dictionary, and if no corresponding alue is found, the second parameter will be set to its variable value.

data = {' user ': 1, ' name ': ' Max ', ' Three ': 4}

Try

Is_admin = data[' admin ']

Except Keyerror:

Is_admin = False

Replace with this:

data = {' user ': 1, ' name ': ' Max ', ' Three ': 4}

Is_admin = data.get (' admin ', False)

Get a subset of a list

Sometimes you just need some of the elements in the list, here are some ways to get a subset of the list.

x = [1,2,3,4,5,6]

#前3个

Print X[:3]

>>> [About]

#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]

60 Character Resolution Fizzbuzz

A short time ago Jeff Atwood promoted a simple programming exercise called Fizzbuzz, which referred to the following questions:

Write a program that prints the number 1 to 100, 3 multiples print "Fizz" to replace this number, 5 multiples print "Buzz", for a number that is both a multiples of 3 and a multiples of 5 to print "Fizzbuzz".

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

For x in range (101):p rint "Fizz" [x%3*4::]+ "Buzz" [X%5*4::]or X

Collection

In addition to Python's built-in data types, the collection module also includes special use cases that are counter useful in some situations. If you've been in this year's Facebook Hackercup, you can even find out what's practical about him.

From collections Import Counter

Print Counter ("Hello")

>>> Counter ({' L ': 2, ' h ': 1, ' E ': 1, ' O ': 1})

Iterative Tools

As with the collections library, there is a library called Itertools, which can be effectively solved for some problems. One of the use cases is to find all the combinations that he can tell you about all the combinations of elements in a group

From Itertools import combinations

Teams = ["Packers", "49ers", "Ravens", "patriots"]

For-game in combinations (teams, 2):

Print game

>>> (' Packers ', ' 49ers ')

>>> (' Packers ', ' Ravens ')

>>> (' Packers ', ' patriots ')

>>> (' 49ers ', ' Ravens ')

>>> (' 49ers ', ' patriots ')

>>> (' Ravens ', ' patriots ')

False = = True

This is a very interesting thing compared to practical techniques, in Python, true and false are global variables, so:

False = True

If False:

Print "Hello"

Else

Print "World"

>>> Hello

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Some tips for beginners in Python