Create week 6 theory.md

Signed-off-by: Andy <[email protected]>

python/week 6 theory.md

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+# Strings
+
+## What are strings
+Strings are character based values, think sentences and letters. Denoted by quotation marks ('' and "" are the same in this context) (e.g. "string") they store letter characters in an array.
+As it is an array with a primary index of zero we can call specific characters by calling specific elements in the array
+e.g.
+word="this is a string"
+print(word[3])
+//this will output s
+
+Like standard arrays the length method can be used to get the length of the array. e.g.
+
+
+##### Multiline strings
+You make them by using triple quotation marks e.g.
+m=""" The quick brown fox
+	jumps over the  lazy
+	dog"""
+
+remember quotation marks don't make a difference
+m=''' The quick brown fox
+		jumps over the lazy
+		dog'''
+- Mutable vs immutable strings
+##### Concatenate strings
+You can combine strings with the "+" operator
+e.g.
+word1="an"
+word2 = "imal"
+word3=word1+word2
+print(word3)
+//this will output animal
+
+##### Checking strings
+You can check whether or not a word, or letter are or are not in a string.
+To check if the word is in you would use the in keyword
+e.g.
+myStr="The quick brown fox jumps"
+print("brown" in myStr)
+// this returns true, and false if it is not there
+
+
+You can also check if a word is **not** in the string
+e.g.:
+myStr="The quick brown fox jumps"
+print("lazy" not in myStr)
+// this returns true, and false if it is not there
+
+len() function can be used  check the length of a character array
+
+# File operations
+
+Python gives a very powerful and versatile user interface that allows you to interact with files very efficiently.
+It follows the general syntax:
+
+	f = open(filename, mode)
+
+
+## Operations
+There are certain modes you can open a file in, and good rule of thumb on their usage is the type of operation you are trying to complete
+### Read
+r: This is to open a file in your program
+r+:This allows you to read and write to a file, it does not overwrite any pre-existing data in the file
+allowing you to primarily read but
+
+	file = open('pyData.txt','r')
+	print(file.readline(1))
+	#This will read the first line in your file, and is one of the methods you can use
+You can use plain read to extract the contents of the file:
+
+	file = open('pyData.txt','r')
+	fileContent=file.read()
+	print(fileContent)
+### Write:
+w: This is to primarily write, giving you full writing privileges allowing you to also overwrite any pre-existing data in the program
+
+	file=open('myData.txt','w')
+	file.write("The quick brown fox jumps over the lazy dog")
+
+w+: This is extended writing, allowing you to create a file if it does not exist ,you can also read data from a given file with the intent to write to it, it will effectively reset the file allowing you to write to it.
+
+
+	file=open('myData.txt','w+')
+	file.write("The quick brown fox jumps over the lazy dog")
+	print(file.read())
+
+### Append:
+a: This is to append, or add to the file without overwriting any pre-existing data
+
+	file=open('myData.txt','a')
+	file.write("The quick brown fox jumps over the lazy dog again")
+
+a+:  This is to append and read data from the file, without overriding any pre-existing data in the file.
+
+	file=open('myData.txt','a+')
+	file.write("The quick brown fox runs from the lazy dog")
+	print(file.read())
+## Create
+x+: this creates the file and will return an error if the file already exists
+e.g.:
+
+	file=open('myData.txt','x')
+	file.write("The quick brown fox jumps over the lazy dog")
+	newfile=open('myData.txt','r')
+	print(myData.read())
+
+