Added help material for Reading and writing files using python3

akashgiricse · akashgiricse · commit cbcc6eaeb40d · 2017-12-21T12:43:45.000+05:30
diff --git a/HelpMaterial/ReadingAndWritingFiles.py b/HelpMaterial/ReadingAndWritingFiles.py
@@ -0,0 +1,112 @@
+#String with a file path
+import os
+os.path.join('usr', 'bin', 'spam')
+# prints string i.e. 'usr/bin/spam'
+
+# join names from a list of filenames to the end of a folder's name:
+myFiles = ['account.txt', 'details.csv', 'invite.docx']
+for filename in myFiles:
+	print(os.path.join('rango/Pictures', filename))
+#prints string i.e.
+# rango/Pictures/account.txt
+# rango/Pictures/details.csv
+# rango/Pictures/invite.docx
+
+
+# current working directory
+print(os.getcwd())
+# prints current directory, in my case it's '/home/rango/ScriptsUsingPython/HelpMaterial'
+os.chdir('/home/rango/Pictures')
+print(os.getcwd()) # prints /home/rango/Pictures
+"""
+# Creating New Folder with os.makedirs()
+os.makedirs('/home/rango/directory1/subdir/subsubdir/mail.txt')
+# will create directory "/home/rango/directory1/subdir/subsubdir/mail.txt"
+"""
+
+# Handling Absolute and Relative Paths
+os.path.abspath('.')
+# returns '/home/rango/ScriptsUsingPython/HelpMaterial'
+
+os.path.abspath('./Pictures')
+# returns '/home/rango/Pictures'
+
+os.path.isabs('.')
+# returns False
+
+os.path.isabs(os.path.abspath('.'))
+# returns True
+
+os.path.relpath('/home/rango', '/home')
+# returns 'rango'
+
+os.path.relpath('/home/rango', '/home/rango/Desktop/Books')
+# returns '../..'
+
+filePath = '/home/rango/Desktop/Books'
+os.path.dirname(filePath)
+# returns '/home/rango/Desktop'
+os.path.basename(filePath)
+# returns 'Books'
+os.path.split(filePath)
+# returns ('/home/rango/Desktop', 'Books') i.e. both dirname and basename.
+filePath.split(os.path.sep)
+# returns ['', 'home', 'rango', 'Desktop', 'Books']
+'/rango/bin'.split(os.path.sep)
+# returns ['', 'rango', 'bin']
+
+# Finding File Sizes and Folder Contenets
+os.path.getsize('/home/rango/Desktop/Books/automate-the-boring-stuff-with-python-2015-.pdf')
+# returns 17449893 in bytes
+os.listdir('/home/rango/Desktop/Books')
+# returns ['DjangoBook', 'automate-the-boring-stuff-with-python-2015-.pdf']
+
+totalSize = 0
+for filename in os.listdir('/home/rango/Desktop/Books'):
+	totalSize = totalSize + os.path.getsize(os.path.join('/home/rango/Desktop/Books', filename))
+print(totalSize) # prints 17453989 
+
+# Checking Path Valitidy
+os.path.exists('/home/rango')
+True
+os.path.exists('/home/rangodango')
+False
+os.path.isfile('/home/rango/Desktop')
+False
+os.path.isfile('/home/rango/Desktop/StartDjango.txt')
+True
+os.path.exists('/media/rango/Windows')
+False # when unmounted
+os.path.exists('/media/rango/Windows')
+True # when mounted
+
+# File Reading/Writing Process
+# Opening Files with the open() function
+helloFile = open('/home/rango/hello.txt') # stores the file object in Read Mode
+helloContent = helloFile.read()
+print(helloContent) # prints content inside the hello.txt file
+
+# writing to files
+# in python intetective shell
+>>> import os
+>>> helloFile = open('hello.txt','w') # open hello.txt in write mode i.e. using 'w'
+>>> helloFile.write('entered into shell \n')
+20
+>>> helloFile.close()
+>>> helloFile = open('hello.txt', 'a') # open fine in append mode so that it will append text and not replace
+>>> helloFile.write('Hello again.')
+12
+>>> helloFile.close()
+>>> helloFile = open('hello.txt')
+>>> content = helloFile.read()
+>>> helloFile.close()
+>>> print(content)
+entered into shell 
+Hello again.
+>>> 
+
+
+
+
+
+
