Graphics Reference
In-Depth Information
2. For each line in the link file, take the source node and the target node
and add them to a list of nodes, checking to make sure that nodes are
not duplicated.
3. Write out the node file.
CSV File and Lists
Pythonhasacomma-separatedvalue(CSV)readerlibrarywithfunctionality
to make it easy to parse
.csv
and tab-delimited (
.txt
) files. The following
code opens the
.csv
file and calls a function to add two nodes per each row:
import csv
# open the link file
with open ("SciFiWriters.txt”, "r") as inputfile:
datareader = csv.reader(inputfile, delimiter="\t")
# skip the header row
next(datareader, None)
# process each row: add source node and target
node
for row in datareader:
addNode(row[0])
addNode(row[1])
The first line imports the Python
csv
library. The next two lines open
the text file
SciFiWriters.txt
as read-only (
"r"
) and set the delimiter
to tab (
"\t"
) as opposed to the default, which is a comma. The file has
a header row (
subject influence
), which is skipped over using
next(datareader, None)
.
The
csv
library turns each row of input into a list data structure. You can
access each field in the list using an
index
(referred to in Python as a
slice
).
The index is an integer, starting at zero for the first item. For example,
consider a data row in the data file:
Stephen King Edgar Allan Poe
The first item is accessed using
row[0]
, which returns
Stephen King
,
while
row[1]
returns
Edgar Allan Poe
,andsoon.Youcanreferencethe
entire row simply using
row
.
