Python 外部数据的读写(cvs,excel)

Posted 2020-10-22 我也想学编程

python 外部数据的读写

来自纪路,Python数据科学实践指南

CSV

• CSV是什么？
  逗号分隔值（Comma-Separated Values，CSV，有时也称为字符分隔值，因为分隔字符也可以不是逗号）
• csv文件读取(str)

import csv

with open("D:/课件/《python数据科学》/data_science_tool_book_code/chapter7/test.csv") as fr:
    rows = csv.reader(fr)
    for row in rows:    #这里要缩进,rows相当于一个流，必须在文件开启时使用
        print(row)
        
######################
[‘PassengerId‘, ‘Pclass‘, ‘Name‘, ‘Sex‘, ‘Age‘, ‘SibSp‘, ‘Parch‘, ‘Ticket‘, ‘Fare‘, ‘Cabin‘, ‘Embarked‘]
[‘892‘, ‘3‘, ‘Kelly, Mr. James‘, ‘male‘, ‘34.5‘, ‘0‘, ‘0‘, ‘330911‘, ‘7.8292‘, ‘‘, ‘Q‘]
[‘893‘, ‘3‘, ‘Wilkes, Mrs. James (Ellen Needs)‘, ‘female‘, ‘47‘, ‘1‘, ‘0‘, ‘363272‘, ‘7‘, ‘‘, ‘S‘]
[‘894‘, ‘2‘, ‘Myles, Mr. Thomas Francis‘, ‘male‘, ‘62‘, ‘0‘, ‘0‘, ‘240276‘, ‘9.6875‘, ‘‘, ‘Q‘]
[‘895‘, ‘3‘, ‘Wirz, Mr. Albert‘, ‘male‘, ‘27‘, ‘0‘, ‘0‘, ‘315154‘, ‘8.6625‘, ‘‘, ‘S‘]
[‘896‘, ‘3‘, ‘Hirvonen, Mrs. Alexander (Helga E Lindqvist)‘, ‘female‘, ‘22‘, ‘1‘, ‘1‘, ‘3101298‘, ‘12.2875‘, ‘‘, ‘S‘]
[‘897‘, ‘3‘, ‘Svensson, Mr. Johan Cervin‘, ‘male‘, ‘14‘, ‘0‘, ‘0‘, ‘7538‘, ‘9.225‘, ‘‘, ‘S‘]

• csv文件读取(字典)

import csv

with open(‘D:/课件/《python数据科学》/data_science_tool_book_code/chapter7/test.csv‘) as fr:
    rows=csv.DictReader(fr)
    for row in rows:
        print(row)

• csv文件写

import csv

with open(‘./csv_tutorial.csv‘,‘a‘) as fw:
    writer=csv.writer(fw)
    writer.writerow([‘c1‘,‘c2‘,‘c3‘])   #同样,必须缩进

EXCEL

• pandas
  一个强大的数据处理库，其中就包括了excel格式的处理
• 读取excel:

import pandas as pd
from pandas import read_excel

pd.set_option(‘display.max_columns‘,4)
pd.set_option(‘display.max_rows‘,6)

df= read_excel(‘D:/课件/《python数据科学》/data_science_tool_book_code/chapter8/A0202.xls‘,‘Sheet1‘)
print(df)

• 写excel

import pandas as pd
from pandas import DataFrame

df=DataFrame([[1,2,3,4],[5,6,7,8],[9,10,11,12]],index=[0,1,2],columns=list("ABCD"))
df.to_excel(‘test.xls‘)