Read text in Python [duplicate]

Question

In the script, for each text file, I check the first two characters. If the first two characters are "[{" which means it is a JSON file, then execute other codes.

However, I have to read the file twice with open(f, 'r', encoding = 'utf-8', errors='ignore' as infile:, which is duplicated. Is there any better way to write this code?

result = [] for f in glob.glob("D:/xxxxx/*.txt"): print("file_name: ",f) with open(f, 'r', encoding = 'utf-8', errors='ignore') as infile: first_two_char = infile.read(2) print(str(first_two_char )) if first_two_char == "[{": with open(f, 'r', encoding = 'utf-8', errors='ignore') as infile: json_file = json.load(infile, strict=False) print(len(json_file)) result.append(json_file) #here appending the list with Jason content print(len(result))

I suppose you could always use seek to reset the cursor rather than reopening the file. — Anthony Labarre
– Anthony Labarre, Commented Aug 17, 2020 at 16:04
Your approach is wrong. Instead of making sure if it's JSON and reading, just TRY reading it as JSON and if it doesn't work, do nothing... — Tomerikoo
– Tomerikoo, Commented Aug 17, 2020 at 16:10
@Tomerikoo Thanks a lot! Yes, you are right. I have changed my code accordingly. It looks better and works well. Thanks again. — rui jiang
– rui jiang, Commented Aug 17, 2020 at 16:59
@AnthonyLabarre Thank you! You really answered my question. Next time when I come across with this issue, I will try seek. — rui jiang
– rui jiang, Commented Aug 17, 2020 at 17:01

tdelaney · Accepted Answer · 2020-08-17 16:10:37Z

You could seek(0) to move the file pointer back to zero. Generally, seeking doesn't work with files opened as text because there is an itermediate cache for bytes-to-string decoding. But seek(0) and seek to end of file work.

result = [] for f in glob.glob("D:/xxxxx/*.txt"): print("file_name: ",f) with open(f, 'r', encoding = 'utf-8', errors='ignore') as infile: first_two_char = infile.read(2) print(str(first_two_char )) if first_two_char == "[{": infile.seek(0) json_file = json.load(infile, strict=False) print(len(json_file)) result.append(json_file) #here appending the list with Jason content print(len(result)) result = []

But really, just attempting the conversion and catching the error is a better way to go. Suppose the first two characters looked okay only by bad luck?

for f in glob.glob("D:/xxxxx/*.txt"): print("file_name: ",f) with open(f, 'r', encoding = 'utf-8', errors='ignore') as infile: try: result.append(json.load(infile)) except json.decoder.JSONDecodeError: pass print(len(result))

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