Add leading Zero Python

Question

I was wondering if someone could help me add a leading zero to this existing string when the digits are sings (eg 1-9). Here is the string:

str(int(length)/1440/60)

// , This isn't a duplicate, since this refers to actually changing the variable's value, not just displaying it differently. The difference is important, since only some of the answers at http://stackoverflow.com/questions/134934/display-number-with-leading-zeros would meet this need. — Nathan Basanese, Jan 15 '16 at 23:14

score 90 · Accepted Answer · answered Feb 07 '14 at 06:16

90

You can use the builtin str.zfill method, like this

my_string = "1"
print my_string.zfill(2)   # Prints 01

my_string = "1000"
print my_string.zfill(2)   # Prints 1000

From the docs,

Return the numeric string left filled with zeros in a string of length width. A sign prefix is handled correctly. The original string is returned if width is less than or equal to len(s).

So, if the actual string's length is more than the width specified (parameter passed to zfill) the string is returned as it is.

answered Feb 07 '14 at 06:16

thefourtheye

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so nice. if u need a trailing 0 only for single digit numbers str.zfill() will just add to those who actually are singe digits. 7 becomes 07, but 10 would stay 10 and not become 010, for example. – Ulf Gjerdingen Nov 05 '21 at 11:16

falsetru · Answer 2 · 2016-01-16T03:52:02.200

27

Using format or str.format, you don't need to convert the number to str:

>>> format(1, '02')
'01'
>>> format(100, '02')
'100'

>>> '{:02}'.format(1)
'01'
>>> '{:02}'.format(100)
'100'

According to the str.format documentation:

This method of string formatting is the new standard in Python 3, and should be preferred to the % formatting ...

edited Jan 16 '16 at 03:52

answered Feb 07 '14 at 06:19

falsetru

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But what if I have a string like `a = "abc"`, then `format(a, "05")` doesn't work – winklerrr Apr 23 '19 at 12:35
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@winklerrr, For non-number, use`format(a, '>05')`. – falsetru Apr 24 '19 at 07:31
@winklerrr that question is not relevant to the original question. This question isn't about validating input, it's about modifying current data. – dmcoding Aug 02 '19 at 18:31
@dmcoding that's why I added a comment (for which I directly got an answer). So what's your problem here? – winklerrr Aug 04 '19 at 11:31

score 16 · Answer 3 · answered Feb 07 '14 at 06:19

16

I hope this is the easiest way:

 >>> for i in range(1,15):
 ...     print '%0.2d' % i
 ...
 01
 02
 03
 04
 05
 06
 07
 08
 09     
 10
 11
 12
 13
 14
 >>>

answered Feb 07 '14 at 06:19

James Sapam

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// , His question was about how to deal with this in an actual variable, not just with printing. – Nathan Basanese Jan 15 '16 at 23:15
2

This is a better answer in general. – Jiminion Aug 30 '16 at 20:09

Add leading Zero Python

3 Answers3

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