Shadowing Practice: [Practice Problems] Regular Expressions (Regex) - Visually Explained - Learn English Speaking with Video
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Have you tried our regular expressions practice exercises?
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If you have, great!
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We're going to work through the solutions now.
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If not, the problems are linked in the description.
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Alright, let's start with problem one.
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In this problem, we want to match all the phone numbers from the bulletin board text.
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Each phone number follows the format.
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A fixed area code, and a hyphen, followed by three digits, another hyphen, and a final four digits.
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Since every phone number starts with the same area code and hyphen, we write the literal characters 1, 2, 3, hyphen directly into the pattern box.
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Next, the middle group of numbers can have any combination of three digits.
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To match this, we use the character class 0 through 9 to match a single digit
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and follow it with the quantifier 3 to match exactly 3.
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Following the character class, we write another literal hyphen.
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To match the last four digits, like the middle three, we use a character class with 0 through 9.
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But to match four digits instead of 3, we use a quantifier of 4.
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Great!
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As we can see, this pattern matches both phone numbers and our bulletin board text.
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Fixed quantifiers like 3 and 4 are ideal when you know the exact length you're looking for.
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Phone numbers, zip codes, product codes, anything with a predictable structure.
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Quantifiers will also be quite useful in problem 2.
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In this problem, we want to write a regular expression to match all the prices in our text string.
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each price starts with a dollar sign followed by one
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or more digits a dot
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and exactly two digits for cents you might be tempted to start by writing the literal dollar sign character
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but in regex dollar sign is a special syntax
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that means end of line
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so it won't match the dollar sign character to match a
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literal dollar sign we put a backslash in front of it after the dollar sign comes the digits before the decimal,
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which we can match using a character class with 0 through 9.
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Since there could be any number of digits before the decimal, we use the plus quantifier to match one or more digits.
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Following this character class, we specify a dot.
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Remember, like the dollar sign, the dot is special syntax, called a wildcard, that matches any single character.
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To use a literal dot character, we need to write a backslash before it.
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Finally, cents always have exactly two digits.
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To match this, we write a character class allowing the digits 0 through 9 and a quantifier of 2.
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Awesome!
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With this pattern, all five prices are matched.
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Before we move on, we've now written the character class containing 0 through 9 several times.
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Since this is such a common pattern, regex syntax actually provides a shorthand for it.
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Instead of explicitly writing the character class, we write backslash d, which also means any digit.
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Awesome, our pattern is now more concise and we still get the same matches.
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We'll use the digit shorthand backslash d again in problem 3.
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In this problem, we want to match all the dates in the text.
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Each date has a month name, a day number, and a four-digit year.
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We'll start by matching the month names.
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Month names are made up of letters, both upper and lowercase, so we'll use a character class of all the uppercase and lowercase letters.
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To match one or more letters, we follow the class with the plus quantifier.
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After the month name comes a literal space.
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After the space, the day can be one digit or two.
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To match exactly one or two digits,
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we use the backslash d shorthand followed by a range quantifier with a lower bound of one and upper bound of two.
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Following the day, we write a literal comma and space.
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Lastly, the year is always four digits, so we write the digit shorthand and a quantifier of four.
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Awesome!
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With that pattern, we've matched all the dates.
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With these practice problems, you've seen how to write patterns for three different data types.
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If you want to go deeper on any of the concepts we used in this video, check out our regular expressions intro video linked in the description.
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We're working on lots more Python explainer videos like this one, so be sure to subscribe so that you don't miss out.
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If you have any questions or topics that you'd like to learn about, let us know in the comments below.
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We'd love to hear from you.
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Thanks for watching!
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Vocabulario y notas de pronunciación para esta lección
Este vídeo tiene 61 frases y 744 palabras para practicar shadowing. La parte hablada dura 5:08. El hablante mantiene un ritmo constante de unas 145 palabras por minuto, cómodo para el shadowing. El 82 % de las palabras está entre las 3.000 más comunes del inglés; conviene repasar el resto antes de empezar.
Vocabulario clave de este vídeo
15 palabras menos comunes del vídeo, con su pronunciación y significado:
- digit /ˈdɪd͡ʒɪt/ (sustantivo) — dígito, cifra. A position in a sequence of numerals representing a place value in a positional number system.
- literal /ˈlɪt(ə)ɹəl/ (adjetivo) — literal. Exactly as stated; read or understood without interpretation; according to the letter; not figurative or metaphorical; following the letter or exact words; not…
- syntax /ˈsɪn.tæks/ (sustantivo) — sintaxis. A set of rules that govern how words are combined to form phrases and sentences.
- bulletin /ˈbʊl.ə.tən/ (sustantivo) — boletín, boletín informativo. A short report, especially one released through official channels to be immediately broadcast or publicized.
- topic /ˈtɑpɪk/ (sustantivo) — tema, tópico. A subject; a theme; a category or general area of interest.
- format /ˈfɔːɹ.mæt/ (sustantivo) — formato. The layout of a publication or document.
- ideal /aɪˈdi(ə)l/ (adjetivo) — ideal, idóneo. Pertaining to ideas, or to a given idea.
- string /stɹɪŋ/ (sustantivo) — cuerda, mecate ("cordel" or "cuerda"). A long, thin and flexible structure made from threads twisted together.
- subscribe /səbˈskɹaɪb/ (verbo) — suscribirse, subscribirse. To write (one’s name) at the bottom of a document; to sign (one's name).
- explicitly (adverbio) — explícitamente, rotundamente. In an explicit manner.
- intro /ˈɪntɹoʊ/ (sustantivo) — intro. An introduction.
- specify /ˈspɛs.əˌfaɪ/ (verbo) — especificar, circunstanciar. To state explicitly, or in detail, or as a condition.
- predictable /pɹəˈdɪktəbləl/ (adjetivo) — predecible, predictible. Able to be predicted.
- lastly /ˈlæstli/ (adverbio) — postreramente, postrimeramente. Used to mark the beginning of the last in a list of items or propositions.
- quantifier /ˈkwɑn.tɪ.faɪ.ɚ/ (sustantivo) — cuantificador. A word, such as all or many, that expresses the quantity of a related noun.
Phrasal verbs que vas a escuchar
- check out (verbo) — investigar, chequear. To record the departure or withdrawal of someone or something (such as guests, employees, books, etc.).
- hear from (verbo) — oír de, oír de parte de. To receive updates or opinions from (someone).
- look for (verbo) — buscar, lambisquear. To seek.
- miss out (verbo) — perdérsela. To miss an experience or lose an opportunity, etc. that should not be missed.
- move on (verbo) — superarlo, seguir adelante. To continue; to proceed; to go on.
Pronunciación a tener en cuenta
El hablante usa 13 contracciones y formas reducidas, como we'll, we're, we've. Dilas en su forma corta, tal como las oyes.
- Los sonidos de “sh” y “zh”: backslash /ˈbækˌslæʃ/, shorthand /ˈʃɔɹthænd/
- Palabras largas — cuida el acento: predictable /pɹəˈdɪktəbləl/, quantifier /ˈkwɑn.tɪ.faɪ.ɚ/
Cómo practicar con este vídeo
- Escucha el vídeo entero una vez sin hablar y anota las palabras que no conoces.
- Haz shadowing frase por frase a velocidad normal, repitiendo cada una hasta que tu ritmo coincida con el del hablante.
- Grábate y compara con el original, prestando atención a palabras como digit, literal, syntax.
Gramática en este vídeo
Las estructuras que más usa el hablante, con las palabras exactas del vídeo:
| Estructura | En el vídeo |
|---|---|
| Voz pasiva be + participio pasado — importa lo que ocurre, no quién lo hace | are linked · might be tempted · are matched |
| Present perfect have/has + participio pasado — una acción pasada que sigue importando ahora | we've now written · we've matched · you've seen |
¿Qué es la Técnica de Shadowing?
Shadowing es una técnica de aprendizaje de idiomas respaldada por la ciencia, desarrollada originalmente para la formación de intérpretes profesionales y popularizada por el políglota Dr. Alexander Arguelles. El método es simple pero poderoso: escuchas audio en inglés nativo y lo repites en voz alta de inmediato, como una sombra que sigue al hablante con solo 1-2 segundos de retraso. A diferencia de la escucha pasiva o los ejercicios de gramática, el shadowing obliga a tu cerebro y músculos de la boca a procesar y reproducir simultáneamente patrones de habla reales. Las investigaciones muestran que mejora significativamente la precisión de la pronunciación, la entonación, el ritmo, el habla conectada, la comprensión auditiva y la fluidez al hablar, convirtiéndola en una de las metodologías más efectivas para la preparación del IELTS Speaking y la comunicación en inglés en el mundo real.