Oct 17: String Slicing, Methods

Learning Objectives

After today's class, you should be able to:

Explain the syntax and meaning of slice operations, with and without indexes.
Name four methods that strings provide, and describe what each method does.
Describe where to find the official documentation for methods of built-in types.

Reminders¶

POGIL Activity¶

Advanced Strings
- If you are absent today, complete this activity at home
- Bring your completed activity to class or office hours

Python Shell in VS Code

VS Code provides a system shell for interacting with the operating system. On Linux, the system shell is usually bash; on macOS, it's usually zsh; and on Windows, it's usually PowerShell. You can't type Python code directly into a system shell. Instead, you can run a Python shell within the system shell.

To start a Python shell, type the python command and press Enter.
To exit a Python shell, type exit() or quit(). Or use a keyboard shortcut:
- On Linux and macOS, press Ctrl+D.
- On Windows, press Ctrl+Z then Enter.

Example Code¶

Model 1

dna = 'CTGACGACTT'
dna[5]
dna[10]
len(dna)
dna[:5]
dna[5:]
dna[5:10]
triplet = dna[2:5]
print(triplet)
dna[-5]
dna[-10]
dna[:-5]
dna[-5:]
triplet = dna[-4:-1]
print(triplet)

Model 2

dna = 'CTGACGACTT'
dna.lower()
print(dna)
lowercase = dna.lower()
print(lowercase)
dnalist = list(dna)
print(dnalist)
dnalist.reverse()
print(dnalist)
type(dna)
dna = dna.split('A')
print(dna)
type(dna)
dna.replace('C', 'g')
print(dna[0])
type(dna[0])
dna[0].replace('C', 'g')
print(dna)