HW Python Basic & pathlib

HW Python Basic & pathlib#

Problem Set 1 [45 points]#

Please use Python 3.6+ (never Python 2).

For other packages: Although I didn’t run all the tests, there will likely be no problem if you use decently recent versions of any packages used in the homework (any version released after 2020).

If you want, you can increase the number of input parameters, make subfunctions, etc., to realize more general functionalities, unless the “instructions” say not to.

This is a set to make you familiar with Python. I had to design this problem set because we mostly do not look at the references and/or do not try to use Google. You may refer to Think Python chapters, and if you cannot find the answer, you must use the Internet.

Problems#

  • Warn: Be aware not to miss any period (.) or quotation marks (' or ").

  1. Write down the results of the following, i.e., write down the results when you print() each of these. [22 point]

    1. a1 = 3 + 4

    2. a2 = 3 + 4.

    3. b = 4 - 2

    4. c = 9 * 8

    5. d = 22 / 3

    6. e = 22 // 3

    7. f = 22 % 3

    8. g1 = 2**2

    9. g2 = 2.**2

    10. g3 = 2**2.

    11. h = "hello"

    12. a1t = type(a1)

    13. a2t = type(a2)

    14. bt = type(b)

    15. ct = type(c)

    16. dt = type(d)

    17. et = type(e)

    18. ft = type(f)

    19. g1t = type(g1)

    20. g2t = type(g2)

    21. g3t = type(g3)

    22. ht = type(h)

  2. Using assert, write a one-line code that [4 point]

    1. checks whether 22 is equal to 3*e + f.

    2. checks whether g2 is equal to g3

  3. Write a one-line code which will define str_quotation, such that print(str_quotation) gives Hello, World! It's me "Hi". (Hint: use the escape charater \, e.g., \".) [4 point]

  4. Write down the results of the following, i.e., write down the results when you print() each of these. [10 point]

    1. L_str = ["a", "b", "c"]

    2. L_num = [1, 2, 3.]

    3. tLs = type(L_str)

    4. tLs0 = type(L_str[0])

    5. tLn2 = type(L_num[-1])

    6. d1 = {'name': ['Halpha', '[Mg II]', '[O III]'], 'intensities': [1, 0.1, 0.2]}

    7. d1_k = list(d1.keys())

    8. d1_e = list(d1.items())

    9. d1_lines = d1['names']

    10. d1_inHa = d1['intensities'][0]

Problem Set 2 [50 points]#

Please use Python 3.6+ (never Python 2).

For other packages: Although I didn’t run all the tests, there will likely be no problem if you use decently recent versions of any packages used in the homework (any version released after 2020).

Here, we will learn how to code in pythonic way. Open your terminal (or Jupyter Notebook) in an empty directory. Start solving the problems after running the code below:

from pathlib import Path
TOPPATH = Path('.')

Problems#

Answer the following questions with a one-line code. [2 points each]

  1. Make a directory named class_01.

    • Hint: newdir = TOPPATH/'class_01' and newdir.mkdir()

  2. Try to make a directory named class_01 again. What error do you see?

  3. How can you avoid this error?

    • Hint: Try using .mkdir(exist_ok=True).

  4. Make a subdirectory assignment_01 inside class_01.

    • Hint: hw01 = newdir/'assignment_01' and do .mkdir().

  5. Make the following directory using one line of code: class_01_appendix/code_snippets.

    • Hint: Use .mkdir(parents=True)

  6. Make a list of all the files and directories in the current directory.

    • Hint: flist = list(TOPPATH.glob('*'))

  7. Find how many files and directories are in the current directory.

    • Hint: len(flist)

  8. Check whether newdir is an existing path.

    • Hint: try newdir.exists()

  9. Check whether newdir is a file or directory.

    • Hint: try newdir.is_file() and newdir.is_dir()

  10. Find the absolute path of newdir.

    • Hint: newdir.resolve()

Answer the following problems [2 points each]

  1. Make an empty file named test00.txt.

    • Hint: set filepath = TOPPATH/'test00.txt' , and use filepath.touch().

  2. Make a simple code that does filepath.touch() if filepath does not exist. Use if.

    • Hint: You can use if filepath.exists(): ...

  3. Make a list that contains the path objects for the 10 files: test01.txt, test02.txt, …, test10.txt.

    • Hint: Initiate a list filelist = [].

    • Hint: use for loop like this

    • for i in range(1, 11):
    filelist.append(TOPPATH / f"test{i:02d}.txt")

    • (You will learn what f"{02:d}" means later. If you want, google “python format string leading zeros”.)

  4. Make 10 files with empty contents, named test01.txt, test02.txt, …, test10.txt.

    • Hint: for fpath in filelist: and use fpath.touch().

  5. Make filelist2 which contains test08.txt, test09.txt, …, test12.txt.

    • Hint: Do as filelist, but change the range part.

  6. Iterate through the paths in filelist2, and make an empty file of that path if it does not exist.

    • Hint: Use a for loop such as for fpath in filelist2.

    • Hint: Use if fpath.exists(): inside the for loop.

  7. Make a list filelist3, which is the union set (list) of filelist and filelist2.

    • There are several ways to do this. One possibility is to use a for loop and append as you did in filelist and filelist2.

    • Another possiblility is to use for fpath in filelist: and use if fpath in filelist2: etc.

    • A simpler pythonic way is to use list(set(filelist).union(filelist2)).

    • Tip: If you want the union of more than 2 lists, you should do list(set().union(a, b, c, d)).

  8. Make a list allfiles of all the txt file paths in your TOPPATH.

    • Hint: allfiles = list(TOPPATH.glob('*.txt'))

  9. Append a fake path tttt00.txt to allfiles.

    • Hint: allfiles.append(TOPPATH/'tttt00.txt')

  10. Sort the list allfiles and print it.

    • Hint: use .sort() appropriately, and just print(allfiles)

  11. Delete allfiles[0].

    • Hint: allfiles[0].unlink()

  12. Delete all the files you created.

    • Hint: Use for loop. Then if fpath.exists(): and fpath.unlink().

Advanced [6 points]

Python has a very useful try-except-finally clause.

Do touch on all the paths in filelist3 again.

Then use

for fpath in filelist3:
    try:
        fpath.unlink()
    except FileNotFoundError:
        continue

  1. Does it run correctly? Are all the files removed?

  2. Think about what each line means. (No answer is required)

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