Strings - Introduction to Computer Science I - Lecture Slides | CS 110, Study notes of Computer Science

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Strings

Strings

• A string is a series of^ characters

• Characters can be referenced by using

brackets

• The first character is at position 0

mystring = “the”

letter = mystring[2] #letter becomes ‘e’

mystring t h e

0 1 2

for loops

mystring = "CS is cool!"

for c in mystring:

print c

index=

while index < len(mystring):

print mystring[index]

index += 1

Slices

• Select a segment of a string

• Specify [start:end]

– include start but do not include end

– if you do not specify start slice starts from the

beginning

– if you do not specify end slices goes to end

mystring=“ CS is cool” print mystring[6:10] print mystring[2:7] print mystring[:4] print mystring[:]

Immutability

• Strings are immutable

– they cannot be changed

string module

• Contains useful methods for strings

http://docs.python.org/lib/string methods.html

• Dot notation allows us to call a method on

a string object

import string mystring=“ adam” string.find(mystring, “ a” ) #returns index of first instance found mystring=“ CS is cool” mystring.split() #result [‘ CS’ ,’ is’ ,’ cool’ ] newstring = mystring.replace(“ CS” , “ Econ” )