What are the commonly used commands in python?

Commonly used commands in Python are: 1. Open csv file; 2. Reorder data [dataframe index]; 3. Find standard deviation; 4. Round up; 5. Hilbert transform; 6. Modify the column names of the dataframe; 7. Sort in ascending or descending order according to a certain column, etc.

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Commonly used commands in Python are:

(1) Open csv file

import pandas as pd 
df=pd.read_csv(r’data/data.csv’)

(2) Reorder dataframe index

data=df.sort_index(axis=0,ascending=False)

(3) Arrange the dataframe in ascending or descending order according to a certain column

data=df.sort([‘date’],ascending=True升序，False降序)

(4) The index of the dataframe starts from 0 again

data=data.reset_index(drop=True)

(5) Draw a picture with the date as the abscissa

import matplotlib.pyplot as plt 
x=data[‘date’]#日期是字符串形式 
y=data[‘close price’] 
plt.plot_date(x,y)

(6) Find the standard deviation

import numpy as np 
np.std

(7) Round down

import math 
math.floor

Round up: math.ceil

(8) Hill Burt transform

from scipy import fftpack 
hx= fftpack.hilbert(price)

(9) Value sorting

data.order()

(10) Difference

data.diff(1)#一阶差分
dataframe 删除元素 
data.drop(元素位置)

(11) Nested array processing method

import itertools 
a = [[1,2,3],[4,5,6], [7], [8,9]] 
out = list(itertools.chain.from_iterable(a))

( 12) Modify column names of dataframe

data.columns=[‘num’,’price’]

(13) Solution to empty rows after importing excel table

import numpy as np 
data= data.drop(data.loc[np.isnan(data.name.values)].index)

(15) Diff usage

1. It is dataframe or series format , just use data.diff() directly

2. It is in list format, first convert it into list format data=data.tolist() and then dif=np.diff(data)

(16) The date type in the dataframe is not in date format and cannot be added or subtracted directly, so it is converted to list format first

t=data.time.tolist() 
date_time = datetime.datetime.strptime(str(t),’%Y-%m-%d %H:%M:%S’) 
date_time=datetime.date(date_time.year,date_time.month,date_time.day) 
past= date_time - datetime.timedelta(days=n*365)

(17) Symbolization

np.sign

(18) Use of dictionary

label={‘11’:’TP’,’1-1’:’FN’,’-11’:’FP’,’-1-1’:’TN’} 
for i in range(len(data1)): 
state=str(int(data1[i]))+str(int(data2[i])) 
result.append(label[state])

(19) Solution to the problem that Chinese characters are not displayed when drawing with plt

from matplotlib.font_manager import FontProperties 
font_set = FontProperties(fname=r”c:\windows\fonts\simsun.ttc”, size=15) 
plt.title(u’中文’, fontproperties=font_set）

(20) Get the running time of the current program

from time import time 
time1=time() 
time2=time() 
print(time2-time1)

Summary: That’s it for this article That’s all, I hope it’s helpful to everyone.

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