Alternative for re.findall for python

Question

I am using an arduino uno and a thermistor to measure the current temperature. I have been using re.findall to find the matching string in line 4, is there an alternative instead of using re.findall that has the same function? as I am not allowed to use re in my project. Thanks

def my_function(port):
    # Set COM Port.....
    ser = serial.Serial(port, 9600, timeout=0,
                        parity=serial.PARITY_NONE, stopbits=serial.STOPBITS_ONE, rtscts=0)

my_function('COM3')

# Set path to my Arduino device
# portPath = my_function
baud = 9600
sample_time = 1  # Takes temperature every 1 second
sim_time = 1  # Graphs 5 data points

# Initializing Lists
# Data Collection
data_log = []
line_data = []

# Establishing Serial Connection
connection = serial.Serial("com3", baud)

# Calculating the length of data to collect based on the
# sample time and simulation time (set by user)
max_length = sim_time / sample_time

# Collecting the data from the serial port
while True:
    line = connection.readline()
    line_data = re.findall('\d*\.\d*', str(line))
    line_data = filter(None, line_data)
    line_data = [float(x) for x in line_data]
    line_data = [(x - 32) * 0.5556 for x in line_data]  # list comprehension to convert line_data temp to celsius
    line_data = [round(elem, 2) for elem in line_data]  # round temp to 2 dp
    if len(line_data) > 0:
        print("The current temperature is:" + str(line_data[0]) + " celsius")
        break

Can you give as a few samples of what `line` is and what you want to extract from it? — Tzane, Apr 25 '22 at 06:53
yep, I have editted my question to include the complete code. line reads the data values from the arduino — Candy Cane, Apr 25 '22 at 07:05
@CandyCane Provide examples of what the `line` variable may contain — Anshumaan Mishra, Apr 25 '22 at 07:08
Unrelated to the current discussion but you should name your function someone better, as a general rule and practice. A good naming convention and habit goes a long way. — Josip Juros, Apr 25 '22 at 08:26

Prox · Answer 1 · 2022-04-25T07:50:45.360

0

Looking at this answer here: https://stackoverflow.com/a/4289557/7802476 A slight modification can also give decimals:

>>> txt = "h3110 23 cat 444.4 rabbit 11 2 dog"
>>> [float(s) for s in txt.split() if '.' in s and s.replace('.','').isdigit()]
>>> [444.4]

Your regex \d*\.\d* will match numbers such as {.2, 2., 2.2,...} but will not match {2} since \. has to be in the number. The above will also do the same.

EDIT: The solution won't handle numbers that are attached to a string {2.2°C} where as the regex does.

To make it handle units as well,

[float(s.replace(f'{unit}', '')) for s in txt.split()
if '.' in s and s.replace('.','').replace(f'{unit}', '').isdigit()]

Where unit can be '°C' or 'F' for temperature.

However, your regex matches all floating point numbers attached to any string. That is, cat2.2rabbit would also return 2.2, not sure if this should be returned.

edited Apr 25 '22 at 07:50

answered Apr 25 '22 at 07:12

Prox

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Since we do not know what the text format is, what is the text also contains units? What if they are comma separated? Try using `txt = "h3110 23 cat 444.4, 32.4C rabbit 11 2 dog"` – Anshumaan Mishra Apr 25 '22 at 07:17
@AnshumaanMishra, If they are comma separated the regex in the question would also fail. If they contain units, then ` [float(s) for s in txt.split() if '.' in s and s.replace('.','').replace(f'{unit}', '').isdigit()]` will hold. Let me edit the answer. – Prox Apr 25 '22 at 07:38

score 0 · Answer 2 · edited Apr 25 '22 at 07:32

0

Since no sample output is given, Here is a code that extracts all valid numbers from the text:

a = "Temperature = 54.3F 62.5, 79999 54.3°C 23.3C"

a+=' '
temp = []
i = 0
while i < len(a):
    if (a[i].isdigit() or a[i] == '.'):
        if a[i] == '.' and '.' in temp[-1]:
            x = a.find(' ', i)
            i = x
            temp.pop()
        elif i == 0:
            temp[-1] += a[i]
        elif len(temp)>0 and a[i-1] == temp[-1][-1]:
            temp[-1] += a[i]
        else:
            temp.append(a[i])
    i += 1
temp = list(map(float, temp)) # Float casting
print(temp)

Output:

['54.3', '62.5', '79999', '54.3', '23.3']

edited Apr 25 '22 at 07:32

Tomalak

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answered Apr 25 '22 at 07:28

Anshumaan Mishra

1,349
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Made a degree symbol for you :) – Tomalak Apr 25 '22 at 07:32
1

...chances are though that the OP simply has a line that has multiple columns and temperature is always in e.g. column 4. I bet something simple as `line.split()[3]` is what they meant to do. – Tomalak Apr 25 '22 at 07:33
@AnshumaanMishra Thank you, yes the output is lik ['73.10', '22.83'] But when I implement your answer I get the following error: TypeError: can't concat str to bytes – Candy Cane Apr 25 '22 at 08:56
@CandyCane What is the value of `line` in your case? – Anshumaan Mishra Apr 25 '22 at 13:31
@AnshumaanMishra example value is [temperature 72.58 22.32 ab\] – Candy Cane Apr 27 '22 at 03:16

Alternative for re.findall for python

2 Answers2