d = """09:56:07:457 -> 7d
09:56:07:841 -> 91
09:56:09:008 -> 02
09:56:09:233 -> 80
09:56:09:345 -> 01
09:56:10:097 -> 80
09:56:10:448 -> 91
09:56:11:424 -> 01
09:56:11:552 -> 01
09:56:12:351 -> 01
09:56:12:607 -> 01
09:56:12:719 -> 01
09:56:13:711 -> 91
09:56:14:574 -> a3"""

import time
import pandas as pd
import numpy as np

import matplotlib.pyplot as plt

data = [i.split('->')[0].strip() for i in d.split("n")]

#replace : with .
data = [i[:8]+"."+i[9:] for i in data]

#add date to beginning
data = ["2001-01-01 " + i for i in data]

#make new dataframe and convert strings to datetime index
df = pd.DataFrame({"ms":data})

#get milliseconds
df["ms"] = pd.to_datetime(df.ms)

#get whole seconds
df["seconds"] = [str(i)[0:19] for i in df["ms"]]
df["seconds"] = pd.to_datetime(df.seconds)
df.index = df.ms
df["bytes"] = [1 for _ in df.seconds]

print(df.head())

                                             ms             seconds  bytes
ms
2001-01-01 09:56:07.457 2001-01-01 09:56:07.457 2001-01-01 09:56:07      1
2001-01-01 09:56:07.841 2001-01-01 09:56:07.841 2001-01-01 09:56:07      1
2001-01-01 09:56:09.008 2001-01-01 09:56:09.008 2001-01-01 09:56:09      1
2001-01-01 09:56:09.233 2001-01-01 09:56:09.233 2001-01-01 09:56:09      1
2001-01-01 09:56:09.345 2001-01-01 09:56:09.345 2001-01-01 09:56:09      1


df['string_seconds'] = [str(i) for i in df.seconds]
df = pd.DataFrame(df.string_seconds.value_counts())
df["seconds"] = pd.to_datetime(df.index)
df1 = df.sort_values('seconds')
df1.index = pd.DatetimeIndex(df1.index)

df1 = df1.iloc[1:]
df1.resample('1S')
df1.plot(x='seconds', y='string_seconds', figsize=(12,3))