如何使用python在csv文件的开头插入一列

Question

Please inform how can I append a column with all 1s at the beginning of the csv file?

orginal:
y   z
1   5
2   6 
3   7

Required:
x  y  z
1  1  5
1  2  6 
1  3  7

Answer 1

If you're using a library like pandas,

df.insert(0, "col1", [100, 100], allow_duplicates=True)

0 indicates the column you're adding. col1 is the name of that column, and the array is the values you're inserting.

As referenced here: https://pandas.pydata.org/docs/reference/api/pandas.DataFrame.insert.html

Answer 2

pandas is a great lib to read csv and manipulate its data. Read the data, add the x-1 column, then dump the content again

import pandas as pd

df = pd.read_csv("export.csv")
df['x'] = 1
df = df[['x', 'y', 'z']]  # reorder cols
df.to_csv("export.csv", index=False)