Python – Strings

A string is a list of characters and, in Python, they are easy to declare using speech marks.

myquote = “Talk is cheap. Show me the code.”

Get the length of a String in Python

Getting the length of a string in python is the same as with a list

len(myquote)

Getting a sub string in Python

You can access individual letters in Python using the index (as per a list) e.g

myquote[3] #returns k

but also you can return a sub string e.g.

myquote[8:13] #returns 'cheap'
myquote[-1] #returns '.' or the last letter.
myquote[:6] #returns 'Talk i'
myquote[5:] #returns 'is cheap. Show me the code.'

This SO answer has a good explanation of slices.

Spliting Strings.

You will often want to split a string into parts.  Maybe its a line from a file that you want to see as words or a date that you would like to split into day, month and year.

myquote= "Task is cheap.  Show me the code"
myquote.split(" ") #returns ['Talk', 'is', 'cheap.', 'Show', 'me', 'the', 'code.']
adate = "23/12/1973"
adate.split("/") #returns ['23', '12', '1973']

Converting text in a Python String

There are a number of different text conversions in Python that convert Strings into a new format e.g.

"HELLO".lower() # returns 'hello'
"world".upper() #returns 'WORLD'
"hello world".title() #returns 'Hello World'

Testing a string for letters, numbers in Python

You can also test a string to see if it contains certain elments or is of a certain type:

"w".isalpha() #returns True
"1".isdigit() #returns True

Replacing Characters in a String

There are a number of ways to replace characters (or sub strings) in a string including regular expressions.  The simpliest way to start with is replace.  The following example will replace any a with a !

word = "once upon a time"
word.replace("a","!")

Other string operations to consider

  • You can trim strings in Python
  • You can join strings normally with a + or use the join method to include a delimiter (seperating character).

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