迭代创建 Pandas DataFrame

Question

I am creating the list as follows:

myList = []
for i in range(0,10):
    val0 = 1  # some formula for obtaining values
    val1 = 2.5
    val2 = 1.8
    myList.append([val0,val1,val2])

How can I do the same loop for pandas DataFrame (ie myList must be a DataFrame ).

Answer 1

Ideally you want to create your DataFrame once you have all the data in place. Slightly modifying your example:

my_df = []
for i in range(0,10):
    d = {
        'val0' : 1,  # some formula for obtaining values
        'val1' : 2.5,
        'val2' : 1.8
    }
    my_df.append(d)

my_df = pd.DataFrame(my_df)

So now my_df is a DataFrame with val0 , val1 and val2 as columns

Answer 2

if i got your question right:

import pandas as pd

myList = []

for i in range(0,10):
    val0 = 1  # some formula for obtaining values
    val1 = 2.5
    val2 = 1.8
    myList.append([val0,val1,val2])

df = pd.DataFrame(myList, columns=['val0','val1','val2'])
print(df)

PS you don't want to do append data to the DataFrame in the loop - it won't be very efficient.

Output:

   val0  val1  val2
0     1   2.5   1.8
1     1   2.5   1.8
2     1   2.5   1.8
3     1   2.5   1.8
4     1   2.5   1.8
5     1   2.5   1.8
6     1   2.5   1.8
7     1   2.5   1.8
8     1   2.5   1.8
9     1   2.5   1.8