week 10 File Reading and Plotting

Question 1

open function

Answer 1

sets up file as file object, retrieves input from file

Question 2

how to open a file

Answer 2

file = open(‘data.txt’)
z = file.readlines()

Question 3

helper functions

Answer 3

created to help set up program (ex: read file)

Question 4

steps of plotting, step 1

Answer 4

import matlab library

import matplotlib.pyplot as plt

Question 5

steps of plotting, step 2

Answer 5

pass value into plot function and show

plt.plot(food)
plt.show()

Question 6

steps of plotting, step 3

Answer 6

saving plot

plt.savefig(‘plot.png’)

Question 7

shorthand notation

Answer 7

short ways to customize plot color and marker

Question 8

customizing ticks

Answer 8

changing the ticks on the plot

plt.xticks(ticks, regions, rotation = ‘20’)
ticks = location you want labeled
regions = new label
rotation = tilt label

Question 9

plt.legend()

Answer 9

makes legend of lines on graph

Question 10

file.close()

Answer 10

closes file, after called no more reads/writes allowed to file

Question 11

file.read()

Answer 11

returns file as a string, you can specify max bytes in ()

Question 12

file.readlines()

Answer 12

returns file lines as elements of a list

Question 13

EOF

Answer 13

end of file

Question 14

file.write()

Answer 14

writes string argument to file

Question 15

mode

Answer 15

indicates how the file is opened and permissions

Question 16

‘r’

Answer 16

open for reading

Question 17

‘w’

Answer 17

open for writing, creates file if one doesn’t exist

Question 18

‘a’

Answer 18

open for appending, creates file if one doesn’t exist

Question 19

’ +’

Answer 19

can be added to letters to specify, update mode (add reading and writing)

Question 20

output buffer

Answer 20

output is buffered by the interpreter before being written on hard drive

Question 21

how to buffer output

Answer 21

f = open(‘myfile.txt’, ‘w’, buffering = 100)

Question 22

f.flush()

Answer 22

clears internal buffer of a file

Question 23

what type should integers be when being written to files?

Answer 23

integers should be converted to strings before being written or appended to files

Question 24

os module

Answer 24

provides access to operating system

Question 25

portability

Answer 25

ability to access an item easily, from multiple locations

Question 26

how do you reduce portability?

Answer 26

by hardcoding file paths as string literals

Question 27

path separator

Answer 27

’\’, ‘/’ separator between character directories

Question 28

os.path.sep

Answer 28

stores path separator for the current operating system

Question 29

os.path.join(“sub”, “output.txt”)… output?

Answer 29

sub\output.txt <– windows
sub/output.txt <– mac

Question 30

os.walk()

Answer 30

walks a directory tree, iterable object in for loop

Question 31

binary data

Answer 31

data stored as sequence of bytes

Question 32

bytes object

Answer 32

used to represent sequence of single-byte values

Question 33

bytes()

Answer 33

creates byte object

Question 34

binary file mode ‘b’

Answer 34

character to open file to binary mode

Question 35

header

Answer 35

sequence constitutes to it, describes bitmaps contents of bytes and unpacking into values

Question 36

struct

Answer 36

module used for packing values into sequences of bytes and unpacking into values

Question 37

struct.pack()

Answer 37

packs values (like str or int) into a sequence of bytes

Question 38

byte order/endianness ‘<’

Answer 38

determines if the most significant or least significant value is first

Question 39

strut.unpack()

Answer 39

unpacks sequence of bytes into new object

Question 40

with statement

Answer 40

can be used to open file, execute statements, and close file

Question 41

context manager

Answer 41

created by with statement, manages use of resources by setting up and tearing down operations

Question 42

what is good practice to open a file?

Answer 42

use with so that it is closed after you’re done using it

Question 43

csv file

Answer 43

text-based file that uses commas to separate fields

Question 44

fields

Answer 44

data items

Question 45

csv module

Answer 45

python library that can be used to read and write csv files

Question 46

how do you read csv files?

Answer 46

csv.reader(csvfile, delimeter = ‘,’)

Question 47

writerow()/writerows()

Answer 47

used to write list of strings into a csv file

Question 48

numpy

Answer 48

python package that provides math computation tools

Question 49

array

Answer 49

multidimensional object with ordered set of elements of the same type

Question 50

shape of array

Answer 50

tuple of array’s dimensions

Question 51

size of array

Answer 51

number of elements in the array

Question 52

axis

Answer 52

direction along each array dimension

Question 53

np.zeros((1, 3))

Answer 53

returns 1 by 3 array of zeros

Question 54

np.full(shape, value)

Answer 54

fills shape with value

Question 55

np.delete(ndarray, index, axis)

Answer 55

returns new array with row, col deleted

Question 56

axis = 0

Answer 56

rows

Question 57

axis = 1

Answer 57

columns

Question 58

ndarray.sort(axis)

Answer 58

sorts in ascending order along specified axis

Question 59

ndarray.ravel()

Answer 59

returns flattened version of given array

Question 60

ndarray.transpose()

Answer 60

transposes array

Question 61

np.array()

Answer 61

creates array

Question 62

matplotlib

Answer 62

package to create plots

Question 63

pyplot

Answer 63

creates figures

Question 64

import structure for matplotlib

Answer 64

import matplotlib.pyplot as plt

Question 65

plt.plot()

Answer 65

line plot function

Question 66

plt.scatter(x,y)

Answer 66

scatter plot function

Question 67

plt.figure(figsize = #)

Answer 67

creates new figure for plot to appear

Question 68

plt.show()

Answer 68

displays figure

Question 69

plt.savefig(name)

Answer 69

saves figure as name

Question 70

plt.title()

Answer 70

titles plot

Question 71

plt.xlabel()

Answer 71

labels x axis

Question 72

plt.ylabel()

Answer 72

labels y axis

Question 73

plt.text(x, y, s)

Answer 73

adds string ‘s’ to coordinates x,y

Question 74

annotate(s, xy, xytext)

Answer 74

links s to coordinates xy

Question 75

legend([names], loc = ‘lower right’)

Answer 75

adds legend with names to specified location (loc)

Question 76

plt.grid(axis = ‘x’)

Answer 76

adds grid lines to specified axis

Question 77

plt.grid(linestyle = ‘–’)

Answer 77

adds grid lines to both axises

Question 78

plt.subplot()

Answer 78

multiple plots in one figure