从.txt文件中读取第N行(Python) [英] Reading every Nth line from a .txt file (Python)
问题描述
我正在编写一个程序，该程序从.txt文件读取时间值和读数，并使用matplotlib将其绘制在网页上.在我的情况下，有很多值，并且该图看起来非常混乱，并且具有成千上万个数据点，它也可能很慢.
I am making a program that reads time values and readings from a .txt file and plots them on a web-page with matplotlib. In my case there are lots of values, and the plot can look very confusing, and with thousands of data points it can also be sluggish.
我目前正在使用以下代码读取.txt行，以将值放入绘图表列表中:
I am currently reading the .txt lines with this code to put the values into plottable lists:
with open('C:/Email/file.txt') as f:
lines = f.readlines()
dates = [str(line.split(';')[0]) for line in lines]
y = [float(line.split(';')[1]) for line in lines]
z = [float(line.split()[2]) for line in lines]
.txt文件的内容如下:
The .txt file content looks like this:
30.05.18_12:27:17; 13.0; -0.0
30.05.18_12:27:18; 14.0; -0.0
30.05.18_12:27:19; 15.0; -0.0
30.05.18_12:27:20; 16.0; -0.0
那么，是否有任何方法可以读取和绘制每N分之一的时间戳和值(例如，每30个就比较理想)?
So, is there any way to read and plot every Nth (for example every 30. would be ideal) timestamp and value?
我一直在研究不同的方法，但是它们似乎令人困惑.
I've been researching different ways but they seem confusing.
我正在考虑的一种解决方案是创建一个计数器，用于对读取行的数量进行计数，然后当计数器为30时，跳过30行，然后在第31行读取并绘制数据.我不知道该怎么做这样做，因为我是Python的新手.
One solution that I was thinking about is to make a counter that counts the amount of read lines, then when the counter is 30, skip 30 the next lines and read and plot the data in line 31. I have no idea how to do this, since I am relatively new to Python.
我们将不胜感激.
以防万一，整个代码在这里:
Just in case, the whole code here:
from flask import Flask
import numpy as np
import matplotlib.pyplot as plt, mpld3
from datetime import datetime
app = Flask(__name__)
@app.route("/")
def hello():
with open('C:/Email/file.txt') as f:
lines = f.readlines()
dates = [str(line.split(';')[0]) for line in lines]
y = [float(line.split(';')[1]) for line in lines]
z = [float(line.split()[2]) for line in lines]
date = [datetime.strptime(x,'%d.%m.%y_%H:%M:%S') for x in dates]
plt.figure(figsize=(10,5))
plt.title('Temperature', fontsize=15)
plt.ylabel('Temperature' + u'\u2103', fontsize=15)
plt.plot_date(date, y, 'r-', label='quadratic')
plt.ylim([10,35])
# Print as HTML
return mpld3.show()
if __name__ == "__main__":
app.run()
编辑:非常感谢MR. F-ROCHE
HUGE THANKS TO MR. F-ROCHE
使用以下代码进行操作:
Got it working with the following code:
@app.route("/")
def hello():
with open('C:/Email/file.txt') as f:
# Counts lines in text (Use later to delete lines every X readings)
# lines = f.readlines()
cpt = 0
all_lines = []
for line in f:
cpt += 1
if cpt == 30:
all_lines.append(line)
cpt = 0
dates = [str(line.split(';')[0]) for line in all_lines]
date = [datetime.strptime(x,'%d.%m.%y_%H:%M:%S') for x in dates]
y = [float(line.split(';')[1]) for line in all_lines]
z = [float(line.split()[2]) for line in all_lines]
plt.figure(figsize=(10,5))
plt.title('Temperature', fontsize=15)
plt.ylabel('Temperature' + u'\u2103', fontsize=15)
plt.plot_date(date, y, 'r-', label='quadratic')
plt.ylim([10,35])
# Print as HTML
return mpld3.show()
推荐答案
类似的内容仅每30行显示一次:
Something like that will only display every 30 lines:
with open('C:/Email/file.txt') as f:
cpt = 0
for line in f:
cpt += 1
if cpt == 30:
print(line)
cpt = 0
您可以将line变量放在这样的列表中:
you can put line variable in a list like this:
all_lines = []
...
all_lines.append(line)
或者用一行代码甚至更好:
or even better with one line of code:
with open('C:/Email/file.txt') as f:
all_lines = [v for i, v in enumerate(f, start=1) if i % 30 == 0]
然后，您可以将其应用于dates，y和z.
Then you can apply that to dates, y and z instead.
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