2-4.3 Intro Python¶

Working with Files¶

4.1 File import in Jupyter Notebooks
4.1 File open() and .read()
4.2 File Read as a list with .readlines()
4.2 File Closing to free resources with .close
4.3 File Read, a line at a time with .readline()
4.3 Remove characters using .strip()
4.4 File .write() with .seek()
4.4 File append mode

> Student will be able to
4.1 Import files in Jupyter Notebooks
4.1 open() and .read() local files in memory
4.1 .read() a specific number of characters
4.2 Use .readlines() to read data from file as a list of lines
4.2 Use .close to free system resources
4.3 Use .readline() to read data from file, one line at a time
4.3 Use .strip() to remove new line characters and other whitespaces
4.4 .write() data to a new local file 4.4 Use .seek() to set file read or write location
4.4 Use file append mode

¶

Concepts

.readline(): read files a line at a time¶

use .readline() to read a line in a file as a string¶

each .readline() moves to the next available line in the file

poem1 = open('poem1.txt', 'r')
poem_line1 = poem1.readline()
poem_line2 = poem1.readline()
poem_line3 = poem1.readline()

¶

Examples

# [ ]Run to download file poem1.txt
!curl https://raw.githubusercontent.com/MicrosoftLearning/intropython/master/poem1.txt -o poem1.txt

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100    56  100    56    0     0    112      0 --:--:-- --:--:-- --:--:--   113

# [ ] review and run example
# open address to file
poem1 = open('poem1.txt', 'r')

# [ ] review and run example
# readline 1, 2, 3
poem_line1 = poem1.readline()
poem_line2 = poem1.readline()
poem_line3 = poem1.readline()

# [ ] review and run example: print the first 3 .readline() values
print(poem_line1 + poem_line2 + poem_line3)

Loops I repeat
loops
loops

# [ ] review and run example printing return value & re-run several times
print(poem1.readline())

loops

# [ ] review and run example to close file in memory- then run previous cell

poem1.close()

¶

Task 1

use readline to get rainbow colors¶

import https://raw.githubusercontent.com/MicrosoftLearning/intropython/master/rainbow as rainbow.txt
open rainbow.txt as rainbow_file as read-only
read the first 3 lines into variables: color1, color2, color3
close rainbow_file
print the first 3 colors

# [ ] import https://raw.githubusercontent.com/MicrosoftLearning/intropython/master/rainbow as rainbow.txt

#Answer:
!curl https://raw.githubusercontent.com/MicrosoftLearning/intropython/master/rainbow -o rainbow.txt

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100    43  100    43    0     0    104      0 --:--:-- --:--:-- --:--:--   105

# [ ] open rainbow.txt as rainbow_text

#Answer:
rainbow_text = open('rainbow.txt', 'r')

# [ ] read the first 3 lines into variables: color1, color2, color3

#Answer:
color1 = rainbow_text.readline()
color2 = rainbow_text.readline()
color3 = rainbow_text.readline()

# [ ] close rainbow.txt

#Answer:
rainbow_text.close()

# [ ] print the first 3 colors

#Answer:
print(color1 + color2 + color3)

red
orange
yellow

¶

Concepts

`.readline()` in a `while` loop¶

>python poem_line = poem1.readline() while poem_line: print(poem_line.capitalized()) poem_line = poem1.readline()

`while .readline()`¶

while loop continues while the readline() value in poem_line returns text
- a string value evaluates as True in the while loop
- an empty string, '', evaluates not True in the while loop
when readline() reaches the end of the file, an empty string is returned

¶

Examples

# [ ] review and run example
# open address to file
poem1 = open('poem1.txt', 'r')

# [ ] review and run example - use a while loop to read each line of a file 
#  remove last character ('\n') and print as upper case
poem_line = poem1.readline()

while poem_line:
    print(poem_line[:-1].upper())
    poem_line = poem1.readline()

LOOPS I REPEAT
LOOPS
LOOPS
LOOPS
I REPEAT
UNTIL I
BREAK

# [ ] review and run example
poem1.close()

¶

Task 2

while .readline() rainbow colors¶

assumes rainbow.txt has been imported in task 1

open rainbow.txt as rainbow_file as read-only
read a color from each line of rainbow_file in a while loop
- print each color capitalized
close rainbow_file

# [ ] open rainbow.txt as rainbow_text as read-only

#Answer:
!curl https://raw.githubusercontent.com/MicrosoftLearning/intropython/master/rainbow -o rainbow.txt 
rainbow_text = open('rainbow.txt', 'r')

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100    43  100    43    0     0    127      0 --:--:-- --:--:-- --:--:--   131

# [ ] read the color from lines of rainbow_text in a while loop
# [ ] print each color capitalized as the loop runs

#Answer:
color = rainbow_text.readline()

while color:
    print(color[:-1].upper())
    color = rainbow_text.readline()

RED
ORANGE
YELLOW
GREEN
BLUE
INDIGO
VIOLET

# [ ] close rainbow_text 

#Answer:
rainbow_text.close()

¶

Concepts

`.readline()` with `.strip()`¶

.strip() whitespace¶

poem_line = poem1.readline().strip()

.strip() removes leading and trailing whitespace, including the '\n' formatting character

¶

Examples

# [ ] review and run example
# open address to file
poem1 = open('poem1.txt', 'r')

# [ ] review and run example - readline while loop without removing '\n'
poem_line = poem1.readline()

while poem_line:
    print(poem_line)
    poem_line = poem1.readline()

poem1.close()

Loops I repeat

loops

loops

loops

I repeat

until I

break

now with `.strip()` to remove leading and trailing whitespace characters¶

# [ ] review and run example - readline with .strip() to remove '\n'
poem1 = open('poem1.txt', 'r')
poem_line = poem1.readline().strip()

while poem_line:
    print(poem_line)
    poem_line = poem1.readline().strip()
    
poem1.close()

Loops I repeat
loops
loops
loops
I repeat
until I
break

¶

Task 3

`.readline()` with `.strip()` rainbow colors¶

assumes rainbow.tx has been imported in task 1

open rainbow.txt as rainbow_file as read-only
read a color from each line of rainbow_file in a while loop
- use .strip to remove the whitespace
- print each color upper case
close rainbow_file

# [ ] open rainbow.txt as rainbow_text as read-only  

#Answer:
!curl https://raw.githubusercontent.com/MicrosoftLearning/intropython/master/rainbow -o rainbow.txt 
rainbow_text = open('rainbow.txt', 'r')

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100    43  100    43    0     0    106      0 --:--:-- --:--:-- --:--:--   107

# [ ] read a color from each line of rainbow_text in a while loop  
# use .strip to remove the whitespace '\n' character 
# print each color upper case 

#Answer:
color = rainbow_text.readline().strip()

while color:
    print(color.upper())
    color = rainbow_text.readline().strip()

RED
ORANGE
YELLOW
GREEN
BLUE
INDIGO
VIOLET

¶

Concepts

`.strip()` with arguments¶

.strip() arguments¶

color = rainbow_messy.readline().strip('*\n*')

.strip('*\n') removes leading and trailing * and \n

¶

Examples

# [ ] review and run example: import rainbow_messy.txt
!curl https://raw.githubusercontent.com/MicrosoftLearning/intropython/master/rainbow_messy -o rainbow_messy.txt

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100    71  100    71    0     0    241      0 --:--:-- --:--:-- --:--:--   256

# [ ] review and run example: open file read only
rainbow_messy = open('rainbow_messy.txt', 'r')

# [ ] review and run example: .readline() without .strip()

color = rainbow_messy.readline()

while color:
    print(color)
    color = rainbow_messy.readline()

**red**

**orange**

**yellow**

**green**

**blue**

**indigo**

**violet**

# [ ] review and run example: strip "*" and newline ('\n')
rainbow_messy = open('rainbow_messy.txt', 'r')

color = rainbow_messy.readline().strip('*\n')

while color:
    print(color)
    color = rainbow_messy.readline().strip('*\n')

rainbow_messy.close()

red
orange
yellow
green
blue
indigo
violet

¶

Task 4

`.strip()` with arguments¶

run import of cities_messy.txt below at least once this notebook session
run open cities_messy.txt below before each test of the while loop cell
edit while loop to strip the colon ':' , newline and spaces
close cities_messy

# [ ] import the file
!curl https://raw.githubusercontent.com/MicrosoftLearning/intropython/master/cities_messy -o cities_messy.txt

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100    77  100    77    0     0    271      0 --:--:-- --:--:-- --:--:--   277

# [ ] run to read the file into memory
cities_messy = open('cities_messy.txt', 'r')

# [ ] edit the code to remove leading or trailing colon, newline and space characters
line = cities_messy.readline().strip(" :\n")

while line:
    print(line)
    line = cities_messy.readline().strip(" :\n")

Beijing
Cairo
London
Nairobi
New York City
Sydney
Tokyo

¶

Task 5

`.strip()` parentheses from poem2_messy¶

import https://raw.githubusercontent.com/MicrosoftLearning/intropython/master/poem2_messy as poem2_messy.txt
open poem2_messy.txt as poem2_messy in read mode
edit while loop to strip the leading and trailing parentheses & print the poem without blank lines
close poem2_messy

# [ ] import https://raw.githubusercontent.com/MicrosoftLearning/intropython/master/poem2_messy as poem2_messy.txt  

#Answer:
!curl https://raw.githubusercontent.com/MicrosoftLearning/intropython/master/poem2_messy -o poem2_messy.txt

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100    75  100    75    0     0    344      0 --:--:-- --:--:-- --:--:--   362

# [ ] open poem2_messy.txt as poem2_messy in read mode

#Answer:
poem2_messy = open('poem2_messy.txt', 'r')

# [ ] edit while loop to strip the leading and trailing parentheses, and newlines
# [ ] print the poem 

#Answer:

line = poem2_messy.readline().strip("()\n")

while line:
    print(line)
    line = poem2_messy.readline().strip("()\n")

while True
I loop
True
loop
True
loop
not True
False
end

2-4.3 Intro Python¶

Working with Files¶

.readline(): read files a line at a time¶

use .readline() to read a line in a file as a string¶

use readline to get rainbow colors¶

.readline() in a while loop¶

while .readline()¶

while .readline() rainbow colors¶

.readline() with .strip()¶

.strip() whitespace¶

now with .strip() to remove leading and trailing whitespace characters¶

.readline() with .strip() rainbow colors¶

.strip() with arguments¶

.strip() arguments¶

.strip() with arguments¶

.strip() parentheses from poem2_messy¶

`.readline()` in a `while` loop¶

`while .readline()`¶

`.readline()` with `.strip()`¶

now with `.strip()` to remove leading and trailing whitespace characters¶

`.readline()` with `.strip()` rainbow colors¶

`.strip()` with arguments¶

`.strip()` with arguments¶

`.strip()` parentheses from poem2_messy¶