DAY 17: Python day 24 & 25

The file system

• create a .txt file
• with open("filename.txt) as keyword
• open() method creates a new file when it doesn't exist
• read and write methods

• setting a mode "r"(read), "w"(write), "a"(append)

• absolute file path: starts from origin
  root: /

• relative file path: starts from working directory
  one step down: ./
  one step up: ../

Intro to CSV(comma-separated values)

csv library

• built-in
• csv.reader(data)

pandas library

• dataframe
• series
• get data in each column by data.columnname or data["columnname"]. Returns a series
• get data in each row by first getting the column value in the row and searching its index.data[data.columnname == item]
• turn series into list through to_list
• turn list into dataframe through pandas.Dataframe(list)
• turn dataframe into csv file through dataframe.to_csv("filename.csv")