학습 및 예측은 맞는데 데이터생성 시 에러발생합니다.

import pandas as pd
train = pd.read_csv("https://raw.githubusercontent.com/lovedlim/inf/refs/heads/main/p4/3_2/train.csv")
test = pd.read_csv("https://raw.githubusercontent.com/lovedlim/inf/refs/heads/main/p4/3_2/test.csv")
# print(train.shape, test.shape)
# print(train.head())
# print(test.head())
train=train.drop('Unnamed: 0', axis=1)
test=test.drop('Unnamed: 0', axis=1)
target=train.pop('TravelInsurance')

# print(train.shape, test.shape)
# print(train.isna().sum().sum())
cols=train.select_dtypes(include="O").columns
from sklearn.preprocessing import LabelEncoder
# le=LabelEncoder()
for col in cols:
  le=LabelEncoder()
  train[col]=le.fit_transform(train[col])
  test[col]=le.transform(test[col])
# print(train.head())  

from sklearn.model_selection import train_test_split
x_tr, x_val, y_tr,y_val=train_test_split(train, target, test_size=0.2, random_state=0)
# x_tr.shape, x_val.shape, y_tr.shape, y_val.shape

from sklearn.ensemble import RandomForestClassifier
rf=RandomForestClassifier(n_estimators=100, max_depth=5, random_state=0)
rf.fit(x_tr,y_tr)
pred=rf.predict_proba(x_val)[:,1]

from sklearn.metrics import roc_auc_score
print(roc_auc_score(y_val, pred))
pred=rf.predict_proba(test)[:,1]
print(pred.shape)

0.8155945419103314
(497,)

그런데 
pd.DataFrame({'y_pred':pred}).reset_index().to_csv('222.csv', index=False)
print(pd.read_csv("222.csv"))
하면 에러가 뜨네요. 왜 그럴까요?
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-99-63ade06c177d> in <cell line: 37>()
     35 pred
     36 pd.DataFrame({'y_pred':pred}).reset_index().to_csv('222.csv', index=False)
---> 37 print(pd.read_csv("222.csv"))

15 frames
/usr/local/lib/python3.10/dist-packages/pandas/io/formats/format.py in <listcomp>(.0)
   1351             formatted = np.array(
   1352                 [
-> 1353                     formatter(val) if not m else na_rep
   1354                     for val, m in zip(values.ravel(), mask.ravel())
   1355                 ]

ValueError: Format specifier missing precision

import pandas as pd
import numpy as np

# 데이터프레임 생성 및 CSV로 저장
df = pd.DataFrame({'y_pred': pred})
df['y_pred'] = df['y_pred'].map('{:.10f}'.format)  # 소수점 형식 명시
df.to_csv('222.csv', index=False)

# CSV 파일 읽기
print(pd.read_csv('222.csv'))