Datetime: date time module, which provides multiple methods to operate date and time

Strftime: format date and time

Get today’s date, yesterday’s date, formatted date

>>> import datetime
>>> today=datetime.date.today()
>>> print today
2018-01-17
>>> formatted_today=today.strftime('%y%m%d')
>>> print formatted_today
180117
>>> yesterday=int(formatted_today)-1
>>> print yesterday
180116

The above content was written on January 17, 2018. Now some problems are found on March 1. When it crosses months, the above code will appear.

yesterday=int(formatted_today)-1

After executing this line of code, the day before March 1 becomes March 0

How to change it?

yesterday = (datetime.date.today() + datetime.timedelta(days=-1)).strftime('%Y%m%d')

Get today’s date first

Then use the timedetla object of datetime, which represents the difference between the two times, datetime.timedelta (days = – 1) means the time of the day before. The day before March 1 is February 28.

Finally, we use strftime to transform the time format

I’ve been looking online for a long time. Either the data frame is transformed into array or the array is transformed into data frame. So here’s a summary. The python generation of mutual transformation is as follows:

Transform dataframe into array
and

df=df.values

Transform array into dataframe

import pandas as pd

df = pd.DataFrame(df)

That’s OK!

First install the memory_profiler and psutil (psutil is mainly used to improve the performance of memory_profile, recommended) (you can use PIP directly)
PIP install memory_profiler
p install psutil
Mprof run test. Py generates a
results. Dat file, such as “mprofile_20160716170529. Dat”, which records the memory along with the change of time
mprof plot
using the commands in the form of pictures showing
the original:
https://blog.csdn.net/baidu_33122327/article/details/79195176

introduce
Magic is a python module to identify the file type
the original project address: https://github.com/ahupp/python-magic

the project integration the Windows needed libraries, directly use this one instead:
https://github.com/julian-r/python-magic
The installation
pip install python-magic-bin
Simple to use
Method 1

>>> import magic
>>> magic.from_file("testdata/test.pdf")
'PDF document, version 1.2'
>>> magic.from_buffer(open("testdata/test.pdf").read(1024))
'PDF document, version 1.2'
>>> magic.from_file("testdata/test.pdf", mime=True)
'application/pdf'

Method 2

>>> f = magic.Magic(uncompress=True)
>>> f.from_file('testdata/test.gz')
'ASCII text (gzip compressed data, was "test", last modified: Sat Jun 28 21:32:52 2008, from Unix)'

A small example of solving a real problem
This example combines the use of Zipfile and Magic

# coding:utf8

import os
from zipfile import ZipFile
import magic

m = magic.Magic()

dir_name = '/home/some_zip/'
for root, dir, files in os.walk(dir_name):
    zipnames = files
    break

for a_zip_name in zipnames:
    print '#' * 80
    print a_zip_name
    with ZipFile(dir_name + a_zip_name) as azip:
        filenames = azip.namelist()
        for i in [10, 20, 30]:
            with azip.open(filenames[i], pwd='zippassword') as afile:
                print m.from_buffer(afile.read())