String formatting, trim from right instead of left

Question

I have a set of strings that I want to format to keep the string at 5 characters. I'm using a line like this (the original strings are sometimes 5 characters, sometimes 6):

ram1 = ram1.astype('|S5')

However, this turns

039410

Into

39410

When I want it to be

03941

Is there a simple way to fix my line of code to do this?

Cheers!

Answer 1

You can use format :

ram1 = '3941'
print '{0:0>5s}'.format(ram1)
## 03941

where the characters after : describe the format (0-padded 5-character long string).

You can also use zfill :

print ram1.zfill(5)
## 03941

In case you need to truncate your string, you can use the following format:

print '{:.5s}'.format('039410')
## 03941

Answer 2

Since you mentioned astype , it appears ram is a NumPy array.

To remove all 0 s from the right size of each value, use np.char.rstrip :

np.char.rstrip(ram, '0')

To preserve just the first 5 bytes for each value,

ram.astype('|S5')

suffices.

---

For example,

import numpy as np
ram = np.array(['039410', '123456', '00000']).astype('|S6')
print(np.char.rstrip(ram, b'0'))
# ['03941' '123456' '']

print(ram.view('|S5'))
# ['03941' '12345' '00000']

---

As Padraic Cunningham points out , if you have an array of strings:

In [209]: ram = np.array(['039410', '123456', '00000']).astype('|S6'); ram
Out[209]: 
array([b'039410', b'123456', b'00000'], 
      dtype='|S6')

and convert the strings to ints, you lose zeros on the left:

In [210]: ram.astype(int)
Out[210]: array([ 39410, 123456,      0])

So do not use astype(int) if you wish to preserve the first 5 bytes of the string.

Answer 3

If you are working with numpy array containing string then astype will work fine.

string = np.array('039410')
print string          
## 039410
string = string.astype('|S5')
print string
## 03941

If you are working on list of strings then you should do this.

str_list = ['039410']
index = 0
for i in str_list:
    i = i[:5]
    str_list[index] = i
    index += 1
print str_list
## ['03941']

If you are working on single string then you just have to do this

str_num = '039410'
str_num = str_num[:5]
print str_num
## '03941'

Answer 4

if the string length is not less than 5 character then you can use the below code

a = "abcdef"

print a[0:5]