webinar-files-2022-01-15

# Webinar: Working with Files 2022 01 15

# open the file and assign to var

# older syntax
f = open("test.txt", "r")
# work with the file
f.close()

# newer syntax, the with/open block
with open("test.txt", "r") as f:
    # work with file
    # two ways to grab contents .read() and .readlines()
    #myString = f.read() # returns it all as one string
    myList = f.readlines() # returns a list of strings by line, much like str.split()

# print(myString)
# print(myList)
for line in myList:
    print(line.rstrip(), end=" ") # rstrip()!

# When dealing with string input in general, and especially from files,
# start to expect that there will be whitespace characters like line returns you don't want!

# The string .strip() and rstrip() methods are great for this!
# It's a good idea to use them almost by default.
# If there's no trailing whitespace, rstrip() doesn't cause any problems

with open("mock_data.csv", "r") as f:
    # print(f.readlines())
    myList = f.readlines()
for line in myList:
    print(line.rstrip().split(",")[3])

# WRITE mode is destructive. It will create a file if it doesn't exist, or overwrite if it does
with open("file123.txt", "w") as f:
    f.write("I am writing to this file.") # from last playhead position...:
    f.write("And I wrote more.") # "I am writing to this file.And I wrote more."

# APPEND mode writes non-destructively, starting at end of file
# let's use new line returns in this version...
with open("file123.txt", "a") as f:
    f.write("\nI am writing to this file.")
    f.write("\nAnd I wrote more.")