2-4.1 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 using the curl command
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 a line at a time
4.3 Use .strip() to remove new line characters
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

Import Files to Jupyter

curl imports files to Jupyter session from a web address

below is a code using curl to import poem1.txt, the code is in a command line interface syntax

>#### !curl https://raw.githubusercontent.com/MicrosoftLearning/intropython/master/poem1.txt -o poem1.txt

The table explains each element of the command above

code	meaning
!	runs command interface supporting curl
curl	enables curl that can download files
https://raw.githubusercontent.com/...	is the address for data file to import
-o	tells curl write data to a file
poem1.txt	name curl will give the file

 

Examples

# [ ] review and run example
!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     32      0  0:00:01  0:00:01 --:--:--    33

 

Concepts

Opening a Local File in read mode

>python poem_file = open('poem1.txt', 'r')

Read mode   'r'

MODE	Description
'r'	read only mode
'w'	write - overwrites file with same name
'r+'	read and write mode
'a'	opens for appending to end of file

open() creates an object that can be addressed in python code

 

Examples

# [ ]Run to open the file in memory as poem_file
poem_file = open('poem1.txt', 'r')

# [ ] run and review code to test if open worked 
# should display name='poem1.txt' and no errors
poem_file

<_io.TextIOWrapper name='poem1.txt' mode='r' encoding='UTF-8'>

 

Task 1

import and open a local file in read mode

1. Import a list of cities using curl
   a. git the list from https://raw.githubusercontent.com/MicrosoftLearning/intropython/master/cities
   b. name the list cities.txt
2. open cities.txt in read mode using a variable = cities_file
3. test that cities_file opened cities.txt with a print statement

# [ ] import cities.txt

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

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100    56  100    56    0     0    284      0 --:--:-- --:--:-- --:--:--   287

# [ ] open cities.txt as cities_file
# [ ] test cities.txt was opened 
#Answer:
cities_file = open('cities.txt', 'r')
cities_file

<_io.TextIOWrapper name='cities.txt' mode='r' encoding='UTF-8'>

 

Concepts

Read a file using .read()

reading text

poem_contents = poem_file.read()

.read() loads the content of the file into memory as a string, including formatting such as new line (\n)

 

Examples

examples expect that the cells that import and open of poem1.txt has been run without a read()

Run the cells that import and open poem1.txt

# [ ] review and run example
poem_contents = poem_file.read()

# [ ] review and run example
# shows the file as a string with formatting characters such as "\n", output should be non-blank
poem_contents

'Loops I repeat\nloops\nloops\nloops\nI repeat\nuntil I\nbreak\n'

# [ ] review and run example
# since .read() loaded the file as a string it can be printed
print(poem_contents)

Loops I repeat
loops
loops
loops
I repeat
until I
break

 

Task 2

read a file

Read the file cities.text that was imported in task 1

1. import cities.txt and open
   a. ensure the code was created and run in task 1 to import cities.txt
   b. create and run code to re-open cities.txt as cities_file
2. read() cities_file into a variable called cities
3. Test the read() by displaying the string contained in cities
4. Test the read() by printing the cities string

# [ ] after import and open of cities.txt in task 1
# [ ] read cities_file as cities
# [ ] display the string: cities

#Answer:
cities = cities_file.read()

# [ ] print the string: cities

#Answer:
print (cities)

Beijing
Cairo
London
Nairobi
New York City
Sydney
Tokyo

 

Concepts

reading a file with .read(n) where n = number of characters to read

each time poem_file.read(10) runs, the next 10 characters are read.

> Note: if .read(10) result is = ''  (or empty string with no characters), it is likely that the end of the file has been reached. Perform a fresh .open() to reset read() to the beginning of the file.

 

Examples

examples expect that the cells that import and open of poem1.txt has been run without a read()

Run the cell at the top of the notebook to import poem1.txt
each line is a different approach to reading and displaying 10 characters of the poem

# [ ] review and run example to read poem1.txt 10 characters at a time
poem_file = open('poem1.txt', 'r')
poem_10char = poem_file.read(10)
print(poem_10char)
poem_10char

Loops I re

'Loops I re'

# [ ] review and run example, + 10 more characters
# reads and displays without storing in a variable
poem_file.read(10)

'peat\nloops'

# [ ] review and run example, + 10 more characters
# reads and stores in variable poem_parts
poem_parts = poem_file.read(10)
print(poem_parts)

loops
loo

# [ ] REPEATEDLY RUN this cell,  + 5 more characters each time run are appended using string addition
# [ ]  consider why no additional text displays after multiple runs
poem_parts += poem_file.read(5)
print(poem_parts)

loops
loops
I 

 

Task 3

digits of pi

read a set number of digits with .read(n)

import, open, read, print

1. import digits_of_pi.txt located at https://raw.githubusercontent.com/MicrosoftLearning/intropython/master/digits_of_pi
2. open as digits_of_pi_text
3. read()the first 4 characters of digits_of_pi_text into a variable called pi_digits
4. print pi_digits
5. add to pi_digits string with string addition
   a. add next 4 characters from digits_of_pi obtained from read()
   b. run the cell multiple times to get more digits of pi

# [ ] digits of pi
# 1. import digits_of_pi.txt

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

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   303  100   303    0     0    804      0 --:--:-- --:--:-- --:--:--   812

# [ ] digits of pi
# 2. open as digits_of_pi_text 
# 3. read() 4 char of digits_of_pi_text to pi_digits variable 
# 4. print pi_digits  

#Answer:
digits_of_pi_text = open('digits_of_pi.txt', 'r')
pi_digits = digits_of_pi_text.read(4)
print(pi_digits)

3.14

# [ ] digits of pi
# 5. add to pi_digits string with string addition  
#   a. add next 4 characters from digits_of_pi obtained from read()  
#   b. run the cell multiple times to get more digits of *pi*

#Answer:
pi_digits += digits_of_pi_text.read(4)
print(pi_digits)

3.14159265358979

 

Concept

.read() returns a string

These strings can be manipulated just like any other string

Boolean tests such as:

• .upper()
• .title()
• string slices, e.g.- cities[3:9]
• etc..

and string methods can be performed such as:

• .isdigit()
• .isalpha()
• etc...

 

Examples

examples expect that the cells that import has been run

it may be necessary to run the cell to import poem1.txt at top of notebook

# [ ] review and run example
poem_file = open('poem1.txt', 'r')
poem_part = poem_file.read(15).upper()
print(poem_part)

LOOPS I REPEAT

# [ ] review and run example
poem_part = poem_file.read(6).title()
print(poem_part)

Loops

# [ ] review and run example
poem_part = poem_file.read(6)
print(poem_part)
print(poem_part.isalpha(), "isalpha() because of `\\n`")
poem_part

loops

False isalpha() because of `\n`

'loops\n'

# [ ] review and run example
poem_file = open('poem1.txt', 'r')
poem_text = poem_file.read()
print(poem_text[8:26])

repeat
loops
loops

 

Task 4

City Initials

Read the file cities.text that was imported in task 1

1. ensure the code was created and run in task 1 to import cities.txt
2. create and run code to re-open cities.txt as cities_file
3. read() cities_file into a variable called cities
4. iterate through the characters in cities a. test if .isupper(), if True append the character to a string variable: initials c. else if (elif) character is "\n", if True append the "\n" to initials
5. print initials

# [ ] compelete the task

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

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100    56  100    56    0     0     94      0 --:--:-- --:--:-- --:--:--    94

cities_file = open('cities.txt', 'r')
cities = cities_file.read()
initials = ""
for letter in cities:
    if (letter.isupper()):
        initials += letter
    elif (letter=="\n"):
        initials += "\n"
print('initials: ',initials)

initials:  B
C
L
N
NYC
S
T

Terms of use   Privacy & cookies   © 2017 Microsoft