Python functions and strings

Question

How would i use a function to grab specific parts of a string?
Say for instance my string consisted of data such as the following: '12345678 123456.78 Doe, John D.' # Data that could be representative of bank software# How do i tell python to make the first chars of the string an int, the second part of the string to be a float and the last part should automatically remain a string right?

for line in file_obj:
    print(line) #would yield something like this '12345678 123456.78 Doe, John D.'

If i had functions like:

def find_balance():
    return float  

def find_acc_num():
    return int
def find_name():
    return str

What would my parameters be? Would for iteration be the best way to solve the problem? I want to be able to change account information (balances and names) as long as the user can supply the correct account number. I am new to using functions and am a bit unsure how to go about doing this...

Thanks in advance for any help i really appreciate it. =D

arshajii · Accepted Answer · 2013-09-29 02:25:17Z

5

You can use str.split() with a maxsplit of 2:

>>> s = '12345678 123456.78 Doe, John D.'
>>> 
>>> v = s.split(None, 2)
>>> int(v[0]), float(v[1]), v[2]
(12345678, 123456.78, 'Doe, John D.')

answered Sep 29, 2013 at 2:25

arshajii

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1 Comment

Trevor Merrifield Over a year ago

Nice, I had no idea there was a maxsplit argument. You learn something new every day.

Trevor Merrifield · Accepted Answer · 2013-09-29 02:58:18Z

1

Probably homework but I am bored

for line in file_obj:
    #Make a list of parts separated by spaces and new lines
    #The second argument says to only split up the first two things
    parts = line.split(None, 2)
    #Assign each value
    theint = int(parts[0])
    thefloat = float(parts[1])
    thestring = parts[3].strip()

You could do this in multiple functions by passing each function the parts if you wanted.

Edit: Changed code to use max length at suggestion of @arshajii . Also stripped the newline at the end of thestring.

edited Sep 29, 2013 at 2:58

answered Sep 29, 2013 at 2:25

Trevor Merrifield

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8 Comments

arshajii Over a year ago

You don't need to do the wasteful rejoining at the end, you just need two splits.

Robert Schneeberger Over a year ago

Thank you! Very helpful. Quick question--does .split() make a list automatically? Or is that just pythons way to represent items separated from a string?

Trevor Merrifield Over a year ago

@RobertSchneeberger it makes a list automatically. In that code line is a string, and its method split returns a list that is then stored into parts.

Robert Schneeberger Over a year ago

This code gives me error could not convert string to float at thefloat = float(parts[1])

Trevor Merrifield Over a year ago

@RobertSchneeberger That error happens if the string is incorrectly formatted. There has to be a number there. The error will be something like ValueError: could not convert string to float: 'something' Does the string make sense? Is your file correct?

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