Looping through text file in a folder with numpy loadtxt

Question

I have several .txt file with similar name, such as data_00, data_01, ..., data_99. I tried to use np.loadtxt in a for loop to read it. Now, I can use r-string to read the values in the text file manually numerical = np.loadtxt(r'file_path\data_0.txt', delimiter=' '), it is working but I am thinking to loop through the files.

So when I tried to use f-string, but it is giving me error "SyntaxError: (unicode error) 'unicodeescape' codec can't decode bytes in position 2-3: truncated \UXXXXXXXX escape"

number = np.arange(100)

for i in number:
    numerical = np.loadtxt(f'file_path\data_{i}.txt', delimiter=' ')

I also tried to use glob to import the value, (code shown below), not it is not giving me the correct values in same order.

file_path = 'file_path' 
file_pattern = "*.txt"

files_list = glob(os.path.join(file_path,file_pattern))

for f in files_list:
    print(f'----- Loading {f} -----')
    numerical = np.loadtxt(f, delimiter=' ', unpack=True)

You didn't make your f-string into an r-string. You need to use `/`, `fr` or `\\ `. — Mad Physicist, Jul 04 '22 at 21:37
@MadPhysicist oh wow I didn't know that, if he at least briefly explained what he's trying to do that would help a lot in solving his problem — nnaem, Jul 04 '22 at 21:42
@nnaem. I think the question is quite clear and unambiguous. I'm currently drafting an answer — Mad Physicist, Jul 04 '22 at 21:43

Mad Physicist · Accepted Answer · 2022-07-04T22:02:00.703

r'file_path\data_0.txt' is a raw (or r-) string. That means that \ is treated as a literal backslash. Without the r prefix, it would have a special meaning as the escape character for strings.

f'file_path\data_{i}.txt' is an f-string. That means that {i} gets special treatment, but \ does not. The escape sequence \U (presumably in your actual path) must be followed by 8 hexadecimal digits that make up the code for a Unicode code point. Clearly this is not what you are looking for.

There are a few solutions available to you:

Escape the \:
```
f'file_path\\data_{i}.txt'
```
This places a single backslash in your string
Make the string both f- and raw:
```
fr'file_path\data_{i}.txt'
```
Stay away from backslashes entirely. Python understands forward slash as the path separator:
```
f'file_path/data_{i}.txt'
```
Have a function, like os.path.join add the path separator for you:
```
os.path.join('file_path', f'data_{i}.txt')
```
Use an r-string, with the format method instead of the newer f-string functionality:
```
r'file_path\data_{}.txt'.format(i)
```

Looping through text file in a folder with numpy loadtxt

1 Answers1