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CS50P Problem Set 6

Lines of Code

In a file called lines.py implement a program that expects exactly one command-line argument, the name (or path) of a Python file, and outputs the number of lines of code in that file.

  • Excluding comments and blank lines
  • If user does not specify exactly one command-line argument, or if the specified file's name does not end in .py, the program should instead exit via sys.exit

Assume that any line that starts with #, optionally preceded by whitespace, is a comment.

  • A docstring should not be considered a comment.

Assume that any line that only contains whitespace is blank. 

# Expect one command line argument
    # If not 1 command line argument
        sys.exit("Two few command-line arguments")
    # If file name does not end in `.py`
        sys.exit("Not a Python file")
    # If file does not exist
        raise FileNotFoundError("File does not exist")

# Count the lines of code
    # Open File
        # If file does not exist
            raise FileNotFoundError("File does not exist")
        # Strip whitespace from start of lines
        # if line starts with #, do not count
        # if a line only contains whitespace = blank

import sys
lstrip()
startswith()
open()
readlines()
raise FileNotFoundError

Pizza Py

Implement a program that expext one command-line argument, the name (or path) of a CSV file in Pinocchio's format, and outputs a table formatted as ASCII art using tabulate, a package on PyPI at pypi.org/project/tabulate.

  • Format the tables using the library's gridformat.

  • If the user does not specify exactly one command-line argument, or if the specified file's name does not end in .csv, of if the specified files does not exist:

    • The program should instead exit via sys.exit.

import csv
import sys
from tabulate import tabulate
tabulate(table, headers="keys", tablefmt="grid")
reader = csv.DictReader(file)
for row in reader:
    table.append(row)
except FileNotFoundError:
    raise FileNotFoundError("File does not exist")

Scourgify

Implement a program that expects the user to provide two comand-line arguments:

  • The name of an existing CSV file to read as input, whose columns are assumed to be, in order, name and house, and
  • The name of a new CSV to write as output, whose columns should be, in order, first, last, and house.

If the user does not provide exactly two command-line arguments, or if the first cannot be read, the program should exit via sys.exitwith an error message.



import csv
import sys
clean_data(input_csv, output_csv)
with open(input_csv, "r") as input_file, open(output_csv, "w", newline='') as output_file:
for row in reader:
last, first = row["name"].strip('"').split(",")
house = row["house"]
writer.writerow({"first": first.strip(), "last": last.strip(), "house":house})
except FileNotFoundError:
    sys.exit(f"Could not read file {input_csv}")

CS50P P-Shirt

Implement a program that expects exactly two command-line arguments:

  • in sys.argv[1], the name (or path) of a JPEG or PNG to read (i.e, open) as input
  • in sys.argv[2], the name (or path) of a JPEG or PNG to write (i.e, save) as output

The program should then overlay shirt.png (which has a transparent background) on the input after resizing and cropping the input to be the same size, saving the result as its ouput.

  1. Open the input with Image.open, per pillow.readthedocs.io/en/stable/reference/Image.html#PIL.Image.open

  2. Resize and crop the input with ImageOps.fit, per pillow.readthedocs.io/en/stable/reference/ImageOps.html#PIL.ImageOps.fit, using default values for method, bleed, and centering

  3. Overlay the shirt with Image.paste, per pillow.readthedocs.io/en/stable/reference/Image.html#PIL.Image.Image.paste

  4. Save the result with Image.save, per pillow.readthedocs.io/en/stable/reference/Image.html#PIL.Image.Image.save.


The program should instead exit via sys.exit:

  • if the user does not specify exactly two command-line arguments,
  • if the input’s and output’s names do not end in .jpg, .jpeg, or .png, case-insensitively,
  • if the input’s name does not have the same extension as the output’s name, or
  • if the specified input does not exist.

Assume that the input will be a photo of someone posing in just the right way, so that, when they’re resized and cropped, the shirt appears to fit perfectly. 

import os
from PIL import Image, ImageOps
import sys
# Ensure files have supported extensions
if not any(input_img.endswith(ext) for ext in extensions):
    sys.exit("Invalid input")
# Ensure input and output files extensions match
if os.path.splitext(input_img)[1] != os.path.splitext(output_img)[1]:
    sys.exit("Input and Output have different extensions")
with Image.open(input_img) as image, Image.open("shirt.png") as shirt:
    # Resize the input image to fit shirt size
    size = shirt.size
    image = ImageOps.fit(image, size)

    # Paste the shirt image onto the resizer input image using shirt as a mask
    image.paste(shirt, (0, 0), shirt)

    # Save final image
    image.save(output_img)