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Mathematica > Core Language > String Manipulation > String Operations >

StringCases

StringCases["string", patt]
gives a list of the substrings in "string" that match the string expression patt.

StringCases["string", lhs->rhs]
gives a list of the values of rhs corresponding to the substrings that match the string expression lhs.

StringCases["string", p, n]
includes only the first n substrings that match.

StringCases["string", {p₁, p₂, ...}]
gives substrings that match any of the p_i.

StringCases[{s₁, s₂, ...}, p]
gives the list of results for each of the s_i.

MORE INFORMATION

String expressions can contain any of the objects specified in the notes for StringExpression.

With the default option setting Overlaps->False, StringCases includes only substrings that do not overlap. With Overlaps->True it includes substrings that overlap.

With Overlaps->All, multiple substrings that match the same string expression are all included. With Overlaps->True, only the first such matching substring at a given position is included.

Setting the option IgnoreCase->True makes StringCases treat lowercase and uppercase letters as equivalent.

StringCases["string", RegularExpression["regex"]] gives substrings matching the specified regular expression.

StringCases[s, lhs:>rhs] evaluates rhs only when the pattern is found.

Basic Examples (2)

Find the substrings matching a pattern:

Return only the named wild-card character in each substring:

Find the substrings matching a pattern:

Return only the named wild-card character in each substring:

Use string patterns:

Use a regular expression:

Use pattern matching for dates:

Mixed regular expressions and string patterns:

Rules to extract values corresponding to matching substrings:

Include only the two first strings that match:

Occurrences in either substring:

StringCases automatically threads over lists of strings:

Find all substrings "cat", including use of uppercase letters:

Find all runs of two or more letters starting with the letter a:

Allow overlaps between the substrings:

Allow multiple substrings to start at the same character as well:

Applications (3)

Extract phone numbers from a text:

Find the sequence of section numbers in the U.S. Constitution:

Find the numbers of amendments to the Constitution:

Primes whose digits are all consecutive:

Properties & Relations (2)

StringCount gives the number of matching substrings:

The length of matching substrings:

Use StringPosition to get the position of matching substrings:

Check:

Possible Issues (1)

Use :> rather than -> if the right-hand side of a rule contains string operations:

Using -> in such cases leads to immediate evaluation and possible error messages:

Neat Examples (1)

Find the sequence of words in the U.S. Constitution:

Total number of words:

Number of distinct words:

Logarithmic frequency distribution of words:

Ten most common words:

Cases StringPosition StringCount StringReplace StringFreeQ StringReplaceList Characters StringExpression RegularExpression SequenceAlignment

String Patterns

Special Characters

Working with String Patterns

Language Overview

Linguistic Data

Processing Textual Data

String Manipulation

String Operations

String Patterns

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