pyplot module of matplotlib Library

1. Draw line chart

plot(x,y)#x. Y can be an expression
xlabel("title_name"，fontsize=14)#Set x,y labels
tick_params("both",labelsize=14)#Set both of x y scale
axis([x_min,x_max,y_min,y_max])#Set axis range
fill_between(x,y1,y2,facecolor='bule',alpha=0.1)#Fill two wire

2. scatter plot

scatter(x_values,y_values,c=y_values,cmap=plt.cm.Blues,edgecolor='none',s=40,alpha=0.5)#cm method can set color mapping; edgcolor is contour color; c is scatter color; alpha is transparency
savefig('fil_name.png',bbox_inches='tight') #Automatically save the generated map and cut off the blank
axes().get_xaxis().set_visible(Fasle) #Hide axis
figure(figsize=(10,6)) #Drawing window size

pygal Library

bar=Bar()#Bar class, creating bar instances
bar.x_label=[] #Set image parameters
bar.add(' Label ',frequencies) #Frequency is the input value
bar.renger_to_file('  .svg') #Save results in svg format

CSV module

 import csv
 with open(filename) as f:
    reader=csv.reader(f)#Create reader object
    header_row=next(reader)#Returns the next line of the file. The first call result is the header
    dates,highs=[],[]
    for row in reader:
        high=int(row[1])
        date=datetime.strptime(row[0],"%Y-%m-%d")#Read the time line in CVS
        dates.append(date)
        highs.append(high)

Autofmt? Xdate()? Automatically adjust X-axis labels to avoid overlap
How to deal with data missing
1. Use try except to handle exceptions
2. Use continue
3.remove()
4.del

Json module

Json.dump (number, f obj) ා two arguments: the data to be stored nmber, and the file object f obj
json.load (f obj) loads the information in the. json file

Mapping the world's population

world_populations.py

import pygal
import pygal.maps.world
from country_codes import get_country_code
from pygal.style import  RotateStyle

filename='population_data.json'
with open(filename) as f:
    pop_data=json.load(f)
cc_populations={}#Create a dictionary with population
for pop_dict in pop_data:
    if pop_dict['Year']=='2010':
        cuntry_name=pop_dict['Country Name']
        population=int(float(pop_dict['Value']))
        code=get_country_code(cuntry_name)
        if code:
            cc_populations[code]=population

cc_pops_1,cc_pops_2,cc_pops_3={},{},{}#Group by number of people
for cc,pop in cc_populations.items():
    if pop<10000000:
        cc_pops_1[cc]=pop
    elif pop<1000000000:
        cc_pops_2[cc]=pop
    else:
        cc_pops_3[cc]=pop
wm=pygal.maps.world.World()#Create a Worldmap instance
wm_style=RotateStyle('#336699')
wm=pygal.maps.world.World(style=wm_style)#pygal.Worldmap() does not exist
wm.title='World Popolations in 2010'
wm.add('0-10m',cc_pops_1)
wm.add('10m-1bn',cc_pops_2 )
wm.add('>1bn',cc_pops_3 )
wm.render_to_file('world_population.svg')


country_code.py
from pygal.maps.world import COUNTRIES  #pygal.i18n no longer exists, find country code
def get_country_code(country_name):
    '''Return country code according to specified country'''
    for code,name in COUNTRIES.items():#COUNTRIES country name - country code pair
        if name==country_name:
            return code
    return  None

Use API(requests package)

API web application interface for program interaction to request specific information using aggregate URL
requestPython interacts with websites

import requests
import pygal
# Make an API call, and store the response.
url = 'https://api.github.com/search/repositories?q=language:python&sort=stars'
r = requests.get(url)#Store response object in variable r
print("Status code:", r.status_code)status_code Verify that the request was successful

# Change the API response value. json format to Python dictionary format
response_dict = r.json()
print("Total repositories:", response_dict['total_count'])

# Explore warehouse information
repo_dicts = response_dict['items']#The items value is a list containing many dictionaries, each of which contains warehouse information

names, plot_dicts = [], []
for repo_dict in repo_dicts:
    names.append(repo_dict['name'])
    
    plot_dict = {
        'value': repo_dict['stargazers_count'],
        'label': repo_dict['description'],
        'xlink': repo_dict['html_url'],
        }
    plot_dicts.append(plot_dict)