Assessment 3 Flashcards
open a file
my_file = open(‘filename’, ‘access mode’)
close a file
my_file.close()
access modes for reading
r or rt
access modes for writing
wt or w
access modes for appending
at or a
reading/writing in binary format
rb or wb
return the whole file in one big string
file_handle.read()
returns a single line of the file in a string each time
file_handle.readline()
where does file_handle.readline() set the cursor to
the next line
move the cursor manually
file_handle.seek()
how to loop over a file
for line in file_handle:
print(line)
writes a single string into the file
.write()
file_handle.write(‘dfdfdf\n’)
writes a list of strings into the file ~ doesn’t add new line characters (or anything else) in between
.writelines()
using a content manager:
with open(“filename”, “access mode”) as file_handle:
when using a content manager, do I need to close it
no, once leaving the indentation from the header, the file is automatically closed by python
what does buffered mean
files aren’t updated until you close the file object in python
what do you put under the try block
you write the code that you expect may throw an error
what do you put under the except block
code to execute if an error occurs
what do I import to deal with csv files
import csv
parameters for csv.reader
csv.reader(file_object, delimiter = ‘,’)
what are the parameters for csv.DictReader
csv.DictReader(file_object,fieldnames)
if the filename parameter for csv.DictReader is not specified
the keys default to the first row
what are the parameters for csv.writer
csv.writer(file_object, delimiter = ‘,’, lineterminator = ‘\n’)
how should the filenames parameter be passed in for csv.DictReader
reader = csv.DictReader(my_file, fieldnames = [‘word’, ‘num’])
what is the data type of output
with open("example.csv") as my_file:
reader = csv.DictReader(my_file)
output = [ line for line in reader]list
example of using sorted to sort a list of lists by the third index
sorted(aList, key = lambda x:x[2], reverse = True)
string that groups elements together and tells python to ignore any time the delimiter appears inside
quotechar of a CSV file
default value for the quotechar is :
double quote (“)
quotechar can be a parameter in
csv.reader()
convert a listed list into a dictionary in one line
other_data = [{data[0][0]: i, data[0][1]:j} for i,j in data[1:J]]
parameters for csv.DictWriter
csv.DictWriter(file_object, fieldnames)
JSON stands for
javascript object notation
JSON uses javascript syntax but it is
text only
True and False in python are ___ in javascript
true and false
None in python is ___ in javascript
null
object in Json is a ___ in python
dict
array in JSON is a ___ in python
list
string in JSON is a ___ in python
str
number (int) in JSON is a ___ in python
int
number (real) in JSON is a ___ in python
float
true in JSON is a ___ in python
True
false in JSON is a ___ in python
False
null in JSON is a ___ in python
None
Json to python is called
deserialization
python to JSON is called
serialization
dict in python is ___ in JSON
object
list, tuple in python is ___ in JSON
array
str in python is ___ in JSON
string
int, long, float in python is ___ in JSON
number
True in python is ___ in JSON
true
False in python is ___ in JSON
false
None in python is ___ in JSON
null
JSON module method that translates the data in a json file into a python dictionary
.load()
json2dict = json.load(open(‘jsonfilename.json’, ‘rt’))
JSON module method that translates a string of JSON code, turns it into a python dictionary
.loads()
jsonstring2dict = json.loads(‘jostling’)
JSON module methods that takes a python dictionary and “dumps” it into a Json file.
.dump()
json.dump(the dictionary.open(‘jsonfile.json’, ‘wt’)).
what does .dump() return?
nothing. Instead it creates a json file in your current directory.
JSON module methods that takes a python dictionary and turns it into a single string
.dumps()
dict2jsonstring = json.dumps(the dictionary)
what is XML?
extensible markup language
xml is a way to
store and transport data
what is a closing tag
>
a root is the
first unique tag
what does an attribute tag look like with the tag name = section and attributes name and location
what is the required import for XML
import xml.etree.ElementTree as ET
how do you create an ElementTree object
tree = ET.parse(‘filename.xml’)
find the root of an xml
root = tree.getroot()
get the list of tagname elements
taglist = treefindall(“tagname”)
finding the first instance of a tagname /subtag within tagname?
tag.find()
finding the text between tags?
tag.find().text
create an element:
root = ET.Element(“rootname”)
create a child element:
child = ET.Element(“child name”)
append a child element to the root
(root.append(child))
how to add attributes to your elements
root.attrib[‘attribute name’] = str(attribute value)
add text to your elements
root.text = “text”
HTML stands for
hypertext markup language
difference between HTML and XML
XML is for data exchange/storage and HTML is mostly for Data display
