Fix pandas EmptyDataError after a Tkinter file dialog: reset the file pointer with seek(0) for reliable read_csv

Learn why pandas read_csv fails with EmptyDataError after a Tkinter file dialog when chardet consumes a file-like object, and how seek(0) resets the stream.

Fixing pandas EmptyDataError after Tkinter file selection: why file-like objects bite and how to reset them

Introduction

After selecting a data file via Tkinter’s filedialog and piping it into pandas, everything behaves—until the source is anything but .xls or .xlsx. Then pandas throws EmptyDataError: No columns to parse from file. The root cause isn’t pandas parsing logic. It’s how the file is being passed and what happened to it just before parsing.

The failing pattern

The issue appears when a path from askopenfilename is opened in binary mode, inspected with chardet.read(), and then handed to pandas.read_csv without rewinding the stream. This pattern silently works for Excel, but fails for CSV/TSV-like inputs.

from tkinter import filedialog
import pandas as pd
import chardet
def pick_and_load():
    chosen_path = filedialog.askopenfilename(
        filetypes=[("DPT files", "*.dpt"), ("Text files", "*.txt"), ("Excel files", "*.xlsx *.xls"), ("XY files", "*.xy")]
    )
    if chosen_path:
        with open(chosen_path, "rb") as fh:
            probed = chardet.detect(fh.read())
            try:
                frame = pd.read_csv(fh, header="infer", sep="[ \t]", engine="python")
            except:
                frame = pd.read_excel(fh)
            print(frame)

What actually goes wrong

In one branch of the code a string path is passed to pandas.read_csv, in the other a file-like object is supplied. A file-like object maintains a read position. Calling fh.read() to detect encoding advances that position to the end of the stream. When read_csv then attempts to parse, there is nothing left to read, which results in EmptyDataError. By contrast, read_excel does not rely on the current file position; it appears to reset or manage it internally, so it succeeds where read_csv fails.

There is also a naming pitfall that makes this easier to miss. Reusing the same identifier for both the filename and the file-like object obscures the transition from a string path to a stream with a mutable position.

The fix

If you read the stream first, reset it before parsing. Calling seek(0) rewinds the file pointer to the beginning so pandas.read_csv sees the full content again.

from tkinter import filedialog
import pandas as pd
import chardet
def pick_and_load_fixed():
    chosen_path = filedialog.askopenfilename(
        filetypes=[("DPT files", "*.dpt"), ("Text files", "*.txt"), ("Excel files", "*.xlsx *.xls"), ("XY files", "*.xy")]
    )
    if chosen_path:
        with open(chosen_path, "rb") as fh:
            guessed = chardet.detect(fh.read())
            fh.seek(0)
            try:
                table = pd.read_csv(fh, header="infer", sep="[ \t]", engine="python")
            except:
                table = pd.read_excel(fh)
            print(table)

Why this matters

Mixing path strings and file-like objects is common in GUI-driven workflows. The moment you introduce pre-processing that consumes the stream, pandas.read_csv will only parse what is left at the current position. Being explicit about the file pointer makes CSV and whitespace-separated inputs robust, while Excel continues to work as expected.

Clarity also improves by not overloading one variable to represent both a path and an open handle. Keeping separate names makes it obvious which operations affect the stream and which only manipulate the path. Finally, rather than catching failures from read_csv and retrying with Excel, decide which parser to call based on the file extension.

Wrap-up

If you probe a file object before parsing, always reset it with seek(0) so pandas.read_csv sees the data from the start. Keep distinct variables for a path and a file handle to avoid confusion, and choose parsing functions deliberately instead of falling back via try/except. These small adjustments eliminate EmptyDataError in the described Tkinter workflow and make your data-loading step predictable.