Python Basic Workflow, Shells, Source Code



Python Interpreter



• You don't need to compile Python codes before using them. You execute Python codes using the Interpreter
• Outside of a virtual environment, your interpreter could be called by many names:
◇ python
◇ python2
◇ python3
◇ python3.6
◇ etc.
• Inside a virtual environment, your interpreter will always go by the name python

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Python Interactive Shell



• Also known as REPL (read-eval-print-loop)

# Launch python3 shell
## Outside virtual environment
python3

# Inside virtual environment (venv)
python


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Basic REPL/ Source Workflow


• Try stuff in REPL before you commit it to a file

# In REPL
>>> 8*8
>>> print("Hello World")


• Open editor like sublime
• Copy and paste code from REPL to editor

# In the text editor
print("Hello World!")


• Press ctrl-shift-p, type py, select "Set Syntax:Python"
• Save file as “hi.py”

# Exit REPL
ctrl-d
# or
exit()


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Running a Source Code File



# cd /filedir/
python3 hi.py
echo $?
# Output
## 0


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

REPL vs. Source Code Execution


• The REPL prints ALL return values
• When execute a file, need to explicitly specify to print something out

# REPL reads, evaluates and then print the output
# printing is done automatically
>>> "Hello World"
'Hello World'



Index