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StringPosition
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StringPosition

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StringPosition["string","sub"]

gives a list of the starting and ending character positions at which "sub" appears as a substring of "string".

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StringPosition["string",patt]

gives all positions at which substrings matching the general string expression patt appear in "string".

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StringPosition["string",patt,n]

includes only the first n occurrences of patt.

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StringPosition["string",{patt1,patt2,…}]

gives positions of all the patti.

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StringPosition[{s1,s2,…},p]

gives the list of results for each of the si.

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represents an operator form of StringPosition that can be applied to an expression.

Details and Options

Examples

open allclose all

Basic Examples  (3)Summary of the most common use cases

Find the starting and ending positions at which "XYZ" occurs in a string:

In[1]:=1
✖
https://wolfram.com/xid/0i1ik0b9e-czh
Out[1]=1

Find where any pairs of identical characters occur:

In[1]:=1
✖
https://wolfram.com/xid/0i1ik0b9e-yv2
Out[1]=1

Use the operator form of StringPosition:

In[1]:=1
✖
https://wolfram.com/xid/0i1ik0b9e-39vk2s
Out[1]=1

Scope  (7)Survey of the scope of standard use cases

StringPosition gives substring positions in the form used by functions like StringTake:

In[1]:=1
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https://wolfram.com/xid/0i1ik0b9e-lj5
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1ik0b9e-oom
Out[2]=2

Find the position of the first occurrence of "XYZ":

In[1]:=1
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https://wolfram.com/xid/0i1ik0b9e-ott
Out[1]=1

StringPosition by default includes overlaps:

In[1]:=1
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https://wolfram.com/xid/0i1ik0b9e-epi
Out[1]=1

Use Overlaps->False to exclude overlaps:

In[2]:=2
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https://wolfram.com/xid/0i1ik0b9e-ltk
Out[2]=2
In[1]:=1
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https://wolfram.com/xid/0i1ik0b9e-s9z
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1ik0b9e-ot5
Out[2]=2

Find the position of a subsequence within a DNA sequence:

In[1]:=1
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https://wolfram.com/xid/0i1ik0b9e-c8opr2
Out[1]=1

Use a wildcard in the pattern found in a given biomolecular sequence:

In[1]:=1
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https://wolfram.com/xid/0i1ik0b9e-s8aq0l
Out[1]=1

The "N" is a degenerate letter and is not a wildcard except in biomolecular sequences:

In[2]:=2
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https://wolfram.com/xid/0i1ik0b9e-0doyya
Out[2]=2

Additional wraparound matches may be found in circular biomolecular sequences:

In[3]:=3
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https://wolfram.com/xid/0i1ik0b9e-vct9sc
Out[3]=3

Match only literal degenerate letter occurrences using Verbatim:

In[1]:=1
✖
https://wolfram.com/xid/0i1ik0b9e-4zcb2d
Out[1]=1

Options  (5)Common values & functionality for each option

IgnoreCase  (2)

Treat "a" and "A" as the same:

In[1]:=1
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https://wolfram.com/xid/0i1ik0b9e-h0b
Out[1]=1

Treat "a" and "A" as different:

In[2]:=2
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https://wolfram.com/xid/0i1ik0b9e-yud
Out[2]=2

Find successive identical characters independent of case:

In[1]:=1
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https://wolfram.com/xid/0i1ik0b9e-cxz
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1ik0b9e-kmc
Out[2]=2

Overlaps  (3)

StringPosition by default includes overlaps:

In[1]:=1
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https://wolfram.com/xid/0i1ik0b9e-c5h
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1ik0b9e-wcd
Out[2]=2

By default, StringPosition only includes one substring starting at any given position:

In[1]:=1
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https://wolfram.com/xid/0i1ik0b9e-o2q
Out[1]=1

With Overlaps->All, it includes all substrings:

In[2]:=2
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https://wolfram.com/xid/0i1ik0b9e-odd
Out[2]=2
In[3]:=3
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https://wolfram.com/xid/0i1ik0b9e-oqv
Out[3]=3

Find positions of subsequences in a circular DNA sequence, including overlaps:

In[1]:=1
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https://wolfram.com/xid/0i1ik0b9e-dpk4k
Out[1]=1

Do not allow overlaps between the subsequences:

In[2]:=2
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https://wolfram.com/xid/0i1ik0b9e-ctcwhz
Out[2]=2

Applications  (2)Sample problems that can be solved with this function

Find positions of pairs of identical letters in a concatenation sequence:

In[1]:=1
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https://wolfram.com/xid/0i1ik0b9e-i21
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1ik0b9e-rcf
Out[2]=2
In[3]:=3
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https://wolfram.com/xid/0i1ik0b9e-2y
Out[3]=3

Find an analogous curve for triples:

In[4]:=4
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https://wolfram.com/xid/0i1ik0b9e-h3y
Out[4]=4

Find the positions of the word "president" in the US Constitution:

In[1]:=1
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https://wolfram.com/xid/0i1ik0b9e-nkg
In[2]:=2
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https://wolfram.com/xid/0i1ik0b9e-lwk
Out[2]=2

Properties & Relations  (2)Properties of the function, and connections to other functions

Use StringTake to extract substrings found by StringPosition:

In[1]:=1
✖
https://wolfram.com/xid/0i1ik0b9e-gy9
Out[1]=1
In[2]:=2
✖
https://wolfram.com/xid/0i1ik0b9e-s53
Out[2]=2

StringCases by default excludes overlaps:

In[3]:=3
✖
https://wolfram.com/xid/0i1ik0b9e-p3m
Out[3]=3
In[4]:=4
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https://wolfram.com/xid/0i1ik0b9e-cqa
Out[4]=4

Use StringReplacePart to replace at positions found by StringPosition:

In[1]:=1
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https://wolfram.com/xid/0i1ik0b9e-b5t
Out[1]=1
In[2]:=2
✖
https://wolfram.com/xid/0i1ik0b9e-h32
Out[2]=2

Possible Issues  (1)Common pitfalls and unexpected behavior

Lists of string patterns in StringPosition are sometimes not the same as pattern alternatives:

In[1]:=1
✖
https://wolfram.com/xid/0i1ik0b9e-on3
Out[1]=1
In[2]:=2
✖
https://wolfram.com/xid/0i1ik0b9e-rpr
Out[2]=2
In[3]:=3
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https://wolfram.com/xid/0i1ik0b9e-wai
Out[3]=3
Wolfram Research (1991), StringPosition, Wolfram Language function, https://reference.wolfram.com/language/ref/StringPosition.html (updated 2020).
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Wolfram Research (1991), StringPosition, Wolfram Language function, https://reference.wolfram.com/language/ref/StringPosition.html (updated 2020).

Text

Wolfram Research (1991), StringPosition, Wolfram Language function, https://reference.wolfram.com/language/ref/StringPosition.html (updated 2020).

✖
Wolfram Research (1991), StringPosition, Wolfram Language function, https://reference.wolfram.com/language/ref/StringPosition.html (updated 2020).

CMS

Wolfram Language. 1991. "StringPosition." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2020. https://reference.wolfram.com/language/ref/StringPosition.html.

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Wolfram Language. 1991. "StringPosition." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2020. https://reference.wolfram.com/language/ref/StringPosition.html.

APA

Wolfram Language. (1991). StringPosition. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/StringPosition.html

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Wolfram Language. (1991). StringPosition. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/StringPosition.html

BibTeX

@misc{reference.wolfram_2025_stringposition, author="Wolfram Research", title="{StringPosition}", year="2020", howpublished="\url{https://reference.wolfram.com/language/ref/StringPosition.html}", note=[Accessed: 19-June-2025 ]}

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@misc{reference.wolfram_2025_stringposition, author="Wolfram Research", title="{StringPosition}", year="2020", howpublished="\url{https://reference.wolfram.com/language/ref/StringPosition.html}", note=[Accessed: 19-June-2025 ]}

BibLaTeX

@online{reference.wolfram_2025_stringposition, organization={Wolfram Research}, title={StringPosition}, year={2020}, url={https://reference.wolfram.com/language/ref/StringPosition.html}, note=[Accessed: 19-June-2025 ]}

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@online{reference.wolfram_2025_stringposition, organization={Wolfram Research}, title={StringPosition}, year={2020}, url={https://reference.wolfram.com/language/ref/StringPosition.html}, note=[Accessed: 19-June-2025 ]}