Pandas 枚举列意外行为

Question

I'm using python to extract tables from some PDFs with tabula. Every table is then converted to a Pandas DataFrame, and I have to perform some analysis on them. I want to iterate every column to see if they contain a particular string, but I noticed an unexpected behavior in one particular df (at least I'm not able to understand what's going on).

This are the columns of the DataFrame, obtained with df.columns ( df is the name of the name of the DataFrame):

 Index(['cognome:xxxxnome:xxxxxprovenienza: esterno\r\rcodice fiscale: xxxxx\rdata valutazione neuropsicologica: 25/03/2021\rdata di nascita: 08/09/1955\retà (anni compiuti): 65\rsesso: m\rnumero anni di scolarità: 13', 'unnamed: 0'], dtype='object')

So, from what I see here, the name of the 0-th column should be

'cognome:xxxxnome:xxxxxprovenienza: esterno\r\rcodice fiscale: xxxxx\rdata valutazione neuropsicologica: 25/03/2021\rdata di nascita: 08/09/1955\retà (anni compiuti): 65\rsesso: m\rnumero anni di scolarità: 13'

What I don't understand is that, if I try to iterate through the columns of df , this is what happens:

for i, col in enumerate(list(df.columns)):
    print(f'{i}-th loop, column name = {col}')

Output:

 numero anni di scolarità: 13ogica: 25/03/2021xxxxprovenienza: esterno 1-th loop, column name = unnamed: 0

So here are my questions:

1. Why the index of the 0-th loop is not printed?
2. Why the printed value of col for the 0-th loop is different from the 0-th element of df.columns ?

Some more details about df:

 <class 'pandas.core.frame.DataFrame'> 
 Int64Index: 0 entries 
 Data columns (total 2 columns):  
 #   Column                                
 Non-Null Count  Dtype  
 ---  ------
 --------------  -----   
 numero anni di scolarità: 13  0 non-null      float64  
 1   unnamed: 0                                               
 0 non-null      float64 
 dtypes: float64(2) 
 memory usage: 0.0 bytes

I'm using Jupyter Notebbok with Pandas version 1.2.0

Answer 1

The problem is with the carriage returns \r which your column name is full of. When you print the string, every time a \r is seen, you start from the beginning of the line, overwriting character by character. So the index 0 gets printed, but then overwritten.